WO2012136965A1

WO2012136965A1 - Coupling unit for use with a twisted pair cable and associated apparatuses and methods

Info

Publication number: WO2012136965A1
Application number: PCT/GB2012/000324
Authority: WO
Inventors: Anthony Peyton; Geoff BUTCHER; John Kelly
Original assignee: Cable Sense Limited
Priority date: 2011-04-08
Filing date: 2012-04-05
Publication date: 2012-10-11
Also published as: GB2489752A; EP2694989A1; GB2489752B; GB201106054D0

Abstract

A coupling unit for use with a shielded twisted pair cable. The coupling unit has an interface for physically connecting the coupling unit to a twisted pair cable, a plurality of conductive elements, each conductive element being configured to be electrically connected to a respective conductor of a twisted pair cable, and at least one electrode that is adjacent to one or more conductive elements of the coupling unit. The at least one electrode is configured to transmit a voltage signal to the one or more conductive elements and/or to receive a voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements. The coupling unit may be used in a network monitoring apparatus.

Description

COUPLING UNIT FOR USE WITH A TWISTED PAIR CABLE AND ASSOCIATED

APPARATUSES AND METHODS

This invention generally relates to a coupling unit for use with a twisted pair cable, preferably for use with a shielded twisted pair cable, e.g. of a type widely used in local area networks. This invention also generally relates to apparatuses and methods associated with such a coupling unit. For example, the invention may further relate to a network monitoring apparatus, e.g. for identifying one or more interconnections between network ports within a network and/or for determining the physical condition or state of one or more channels within a network.

Cables which include a plurality of twisted pairs, referred to as "twisted pair cables" herein, are well known. Such cables are commonly used for telecommunications purposes, e.g. computer networking and telephone systems. In the field of telecommunications, twisted pair cables are usually provided without shielding, i.e. as unshielded twisted pair (UTP) cables. However, twisted pair cables containing

shielding ("shielded twisted pair cables" herein) are also known .

In this context, a "twisted pair" is a pair of

conductors, usually a forward conductor and a return conductor of a single circuit, which have been twisted together. The conductors are usually twisted together for the purposes of cancelling out electromagnetic interference from external sources and to minimise cross-talk between neighbouring twisted pairs within a cable comprising a plurality of twisted pairs. In this way, each twisted pair provides a reliable respective communication channel for a signal, usually a differential voltage signal, to be conveyed within the twisted pair. Common forms of unshielded twisted pair cables are category 5 and category 6 unshielded twisted pairs which include eight conductors twisted together in pairs to form four twisted pairs .

The design and construction of twisted pair cables is carefully controlled by manufacturers to reduce noise due to electromagnetic interference and to reduce cross-talk between the twisted pairs within the cables. To this end, each twisted pair in a twisted pair cable normally has a different twist rate (i.e. number of twists per unit length along the cable) from that of the other twisted pairs in the cable. It is also usual for the twisted pairs to be twisted around each other within the cable. Fillets or spacers may be used to separate physically the twisted pairs.

To further reduce crosstalk between twisted pairs within a cable or to reduce crosstalk between separate cables, which is know as alien channel crosstalk, electromagnetic (or

"electric") shielding or screening may be used, which

typically is of electrically conductive material, usually metallic foil.

Within this application, the term "shielded twisted pair cable" is to be interpreted as a twisted pair cable that includes electromagnetic shielding, i.e. shielding for inhibiting an electromagnetic field, e.g. of electrically conductive material. The electromagnetic shielding may include electromagnetic shielding arranged to shield each twisted pair from the other twisted pairs, e.g. with each twisted pair surrounded by its own electromagnetic shielding that shields it from the other twisted pairs, e.g. so as to prevent crosstalk between the twisted pairs. The electromagnetic shielding may additionally, or alternatively, include an outer electromagnetic shielding that surrounds all twisted pairs, e.g. so as to reduce/prevent alien channel crosstalk and/or to shield the twisted pairs from external electromagnetic interference (EMI) . In order to make the electromagnetic shielding effective, it is usually connected to a ground. The terminology used to describe shielded twisted pair cables varies from manufacturer to manufacturer. For

consistency, a shielded twisted pair cable including

electromagnetic shielding arranged to shield each twisted pair from the other twisted pairs but does not include an outer electromagnetic shielding that surrounds all twisted pairs is herein referred to as an "STP" cable (outside of this patent application, such cables can sometimes be referred to as "shielded twisted pair" or "screened twisted pair" cables, but this is avoided in the present application where the term "shielded twisted pair" cable is reserved for identifying a twisted pair cable that includes any form of electromagnetic shielding) . A shielded twisted pair cable including an outer electromagnetic shielding (e.g. foil) that surrounds all twisted pairs but does not include electromagnetic shielding arranged to shield each twisted pair from the other twisted pairs is herein referred to as a "foil/unshielded twisted pair" or "F/UTP" cable. A twisted pair cable including both electromagnetic shielding arranged to shield each twisted pair from the other twisted pairs and an outer electromagnetic shielding that surrounds all twisted pairs is herein referred to as a "screened fully shielded twisted pair" or "S/FTP" cable (sometimes "S/STP" is also used to describe this type of cable) .

Telecommunications networks, e.g. local area networks (LANs), are also well known. Local area networks are typically used to enable equipment such as computers, telephones, printers and the like to communicate with each other and with remote locations via an external service provider. Local area networks typically utilise twisted pair network cables, usually in the form of unshielded twisted pair cables, although in some case shielded twisted pair cables such as STP or F/UTP may be employed. The twisted pair cables generally interconnect network ports within the network to form one or more network lines (or "channels") through which data can be communicated.

The network cables in a local area network are typically connected to dedicated service ports throughout one or more buildings. The network cables from the dedicated service ports can extend through the walls, floor and/or ceilings of the building to a communications hub, typically a communications room containing a number of network cabinets. The network cables from wall and floor sockets within the building and from an external service provider are also usually terminated within the communications room.

A "patch system" may be used to interconnect various network lines of the local area network within the network cabinets. In a patch system, all of the network lines can be terminated within the network cabinets in an organized manner. The terminations of the network lines are provided by the structure of the network cabinets, which are typically organised in a rack system. The racks contain "patch panels", which themselves utilise sets of network ports, typically RJ45-type or screened RJ45-type connector ports, at which the network lines terminate.

Each of the network ports in each patch panel is generally wired to one of the local area network's network lines. Accordingly, each network line is terminated on a patch panel in an organized manner. In small patch systems, all network lines may terminate on the patch panels of the same rack. In larger patch systems, multiple racks are used, wherein different network lines terminate on different racks.

The interconnections between the various network lines are made using "patch" cables, which are typically shielded or unshielded twisted pair cables including four twisted pairs. Each end of a patch cable is terminated by a connector, such as an RJ-45 type connector for inserting into an RJ-45 type connector port as described above. One end of the patch cable is connected to the network port of a first network line and the opposite end of the natch cable is connected to the network port of a second network line. By selectively

connecting the various network lines using the patch cables, a desired combination of network interconnections can be achieved .

Fig. 1 shows a typical patch system organised into a server row, a cross-connect row and a network row, which include four patch panels. Four patch cables are used to interconnect two network lines through the patch system.

Fig. 2 shows an example of a typical patch panel viewed from an edge of the casing of a patch panel. "Fixed", e.g. permanently installed, cables are located on one side of (internally within) the patch panel, in this case shown at the top of the drawing, and the patch cables (aka "patch leads") are located on the opposite side of (outside) the patch panel, in this case shown at the bottom of the drawing. The fixed cables are wired to network ports (aka "patch ports") of the patch panel and, as shown here, not all the network ports of the patch panel necessarily have a patch cable inserted. The network ports are typically an RJ45-type socket or similar socket connector whereas the patch cables typically contain a RJ-45 type plug or similar plug connector. The network port sockets of the patch panel typically have a defined mechanical fixing and in many cases can be demounted from the patch port.

In many businesses, employees are assigned their own computer network access number so that the employee can interface with the companies IT infrastructure. When an employee changes office locations, it is not desirable to provide that employee with newly addressed network port.

Rather, to preserve consistency in communications, it is preferred that the exchanges of the network ports in the employee's old office be transferred to the telecommunications ports in the employee's new location. This type of move is relatively frequent. Similarly, when new employees arrive and existing employees depart, it is usually necessary for the patch cables in the network cabinet (s) to be rearranged so that each employee's exchanges can be received in the correct location .

As the location of employees change, the patch cables in a typical cabinet are often manually entered in a computer based log. This is burdensome. Further, technicians often neglect to update the log each and every time a change is made. Accordingly, the log is often less than 100% accurate and a technician has no way of reading where each of the patch cables begins and ends. Accordingly, each time a technician needs to change a patch cable, that technician manually traces that patch cable between an internal line and an external line. To perform a manual trace, the technician locates one end of a patch cable. The technician then manually follows the patch cable until he/she finds the opposite end of that patch cable. Once the two ends of the patch cable are located, the patch cable can be positively identified.

It takes a significant amount of time for a technician to manually trace a particular patch cable, especially in large patch systems. Furthermore, manual tracing is not completely accurate and a technician may accidently go from one patch cable to another during a manual trace. Such errors result in misconnected patch cables which must be later identified and corrected .

Attempts have been made in the prior art to provide an apparatus which can automatically trace the common ends of each patch cable within local area networks, thereby reducing the labour and inaccuracy of manual tracing procedures.

For example, US Patent Number 5483467 describes a patching panel scanner for automatically providing an indication of the connection pattern of the data ports within a local area network, so as to avoid the manual task of identifying and collecting cable connection information. In one embodiment, which is intended for use with shielded twisted pair cables, the scanner uses inductive couplers which are associated with the data ports. The inductive coupler is disclosed as being operative to impose a signal on the shielding of shielded network cables in order to provide an indication of the connection pattern produced by connection of the cables to a plurality of ports.

In another embodiment of US Patent Number 5483467, the scanner is coupled to each data port by "dry contact" with a dedicated conductor in a patch cable. This is difficult to implement in practice, because most network cables have to meet a particular pre-determined standard in the industry, such as RJ45, in which there is no free conductor which could be used for determining interconnectivity .

US Patent Number 6222908 discloses a patch cable identification and tracing system in which the connectors of each patch cable contain a unique identifier which can be identified by a sensor in the connector ports of a

telecommunications closet. By reading the unique identifier on the connectors of each patch cable, the system can keep track of which patch chords are being added to and removed from the system. Although this system avoids the use of dedicated conductors in the patch cable, it is difficult to implement because it requires use of non-standard patch cables, i.e. patch cables with connectors containing unique identifiers.

International Patent Application Publication Number WO00/60475 discloses a system for monitoring connection patterns of data ports. This system uses a dedicated conductor which is attached to the external surface of a network cable in order to monitor the connection pattern of data ports.

Although this allows the system to be used with standard network cables, it still requires the attaching of dedicated conductors to the external surfaces of network cables and adapter jackets which are placed over the standard network cable .

US Patent Number 6285293 discloses another system and method for addressing and tracing patch cables in a dedicated telecommunications system. The system includes a plurality of tracing interface modules that attach to patch panels in a telecommunications closet. On the patch panels, are located a plurality of connector ports that receive the terminated ends of patch cables. The tracing interface modules mount to the patch panels and have a sensor to each connector port which detects whenever a patch cable is connected to the connector port. A computer controller is connected to the sensors and monitors and logs all changes to the patch cable

interconnections in an automated fashion. However, this system cannot be retrofitted to an existing network and relies on the operator to work in a particular order if the patch cable connections are to be accurately monitored.

International Patent Application Publication Number WO2005/109015, also by the present inventors, which relates to the field of cable state testing, discloses a method of determining the state of a cable comprising at least one electrical conductor and applying a generated test signal to at least one conductor of the cable by a non-electrical coupling transmitter. The reflected signal is then picked up and compared with expected state signal values for the cable, so that the state of the cable can be determined. The

inventors have found that signals coupled to a twisted pair cable by the methods described in O2005/109015 have a tendency to leak out from the twisted pair cable, especially when other twisted pair cables are nearby.

UK patent application GB0905361.2 (published as

GB2468925) , also by the present inventors, describes an invention which relates to apparatuses and methods for coupling a signal to and/or from a cable which includes a plurality of twisted pairs. In particular, this invention relates to coupling a signal to and/or from such a cable by non-contact (capacitive) coupling with the cable. Such signals may be used to determine interconnections, e.g. within a local area network. The disclosure of GB0905361.2 generally relates to a discovery that a twisted pair cable, e.g. an unshielded twisted pair (OTP) cable, provides communication channels which are additional to the respective communication channel provided within each twisted pair in the cable. In particular, it has been found that additional communication channels exist between each combination of two twisted pairs within a twisted pair cable, due to coupling between the twisted pairs. Each combination of two twisted pairs within a twisted pair cable has been termed a "pair-to-pair" combination. Therefore, the additional communication channels may be termed "pair-to-pair" channels. GB0905361.2 discloses that a signal which

propagates along a twisted pair cable between two of the twisted pairs can propagate reliably and over useful

distances, without significantly altering the transmission of signals within the individual twisted pairs. Consequently, the "pair-to-pair" signal can propagate in addition to the differential voltage signals which typically propagate within each twisted pair when the twisted pair cable is in use.

Therefore test signals can be introduced into the "pair-to- pair" channel and these "pair-to-pair" signals can be used to monitor the operation of the network without disrupting the normal operation of the network.

UK patent application GB1009184.1 (published as

GB2480830), also by the present inventors, discloses signal processing apparatuses and methods for use with a plurality of cable lines (aka "network channels" or "network lines") , such as those including one or more twisted pair cables. In particular, GB1009184.1 relates to apparatuses and methods for analysing one or more characteristics of a test signal coupled out from one of a plurality of cable lines. GB1009184.1 presents apparatuses and methods for analysing a

characteristic of a test signal,- which may be a "oair-to-pair" signal to determine whether that test signal has propagated directly to the coupling unit via a single cable line or has propagated indirectly to the coupling unit via crosstalk between different cable lines.

UK patent application GB1018582.5 (which corresponds to International Patent Application PCT/GB2011/001558 ) , also by the present inventors and a copy of which is annexed hereto, discloses apparatuses for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state (i.e. condition) of cable lines in the network.

The content of UK patent applications GB0905361.2, GB1009184.1 and GB1018582.5 is incorporated herein by

reference .

A limitation of the apparatuses and methods disclosed in UK patent applications GB0905361.2, GB1009184.1 and

GB1018582.5, is that these apparatuses and methods are generally designed to be used with unshielded twisted pair (UTP) cables, and may therefore be unsuitable for use with shielded twisted pair cables. For example, the coupling units shown and described in GB0905361.2 have electrodes for coupling a signal into a twisted pair cable that is positioned between the electrodes. Such electrodes would not, in general, be able to transmit/receive a voltage signal to/from a shielded twisted pair cable, since the shielding (e.g. which may surround all twisted pairs in an F/UTP cable, or which may surround the individual twisted pairs in an STP cable) will generally prevent the electrodes from coupling with the twisted pairs, and therefore will generally prevent the electrodes from transmitting/receiving a voltage signal to/from the twisted pairs. The present invention has been devised in Light of the cv^Q consid° ³ ^^{~ < n Q}

In general, the present invention relates to a coupling unit for use with a twisted pair cable, preferably a shielded twisted pair cable, the coupling unit having a plurality of conductive elements, each conductive element being configured to be electrically connected to a respective conductor of a twisted pair cable, and at least one electrode configured to transmit a voltage signal to the one or more conductive elements and/or to receive a voltage signal from the one or more conductive elements by non-contact (preferably

capacitive) coupling with the one or more conductive elements.

In this way, a voltage signal transmitted to the one or more conductive elements can propagate along a twisted pair cable via one or more conductors of the twisted pair cable electrically connected to the one or more conductive elements (e.g. if the coupling unit is physically connected to the twisted pair cable by an interface of the coupling unit) .

Similarly, a voltage signal can be received by the one or more conductive elements after the voltage signal has propagated along a twisted pair cable via one or more conductors of a twisted pair cable electrically connected to the one or more conductive elements (e.g. if the coupling unit is physically connected to the twisted pair cable by an interface of the coupling unit) .

For the avoidance of any doubt, when a signal is described as propagating along a twisted pair cable, it might, but need not, propagate along the entire length of the twisted pair cable.

Advantageously, the coupling unit can be used to transmit/receive a voltage signal, not just to/from the conductors of a UTP cable, but also to/from the conductors of a shielded twisted pair cable. This is because the conductive elements permit the electrodes to couple (indirectly, via the conductive elements) with one or more conductors of the shielded twisted pair cables. As noted above, this was generally not possible with the apparatuses and methods disclosed in UK patent applications GB0905361.2, GB1009184.1 and GB1018582.5, also by the present inventors.

A first aspect of the invention may provide:

a coupling unit for use with a twisted pair cable, preferably a shielded twisted pair cable, the coupling unit having:

an interface for physically connecting the coupling unit to a twisted pair cable;

a plurality of conductive elements, each conductive element being configured to be electrically connected to a respective conductor of a twisted pair cable, if the coupling unit is physically connected to the twisted pair cable by the interface; and

at least one electrode that is adjacent to one or more conductive elements of the coupling unit, the at least one electrode being configured to transmit a voltage signal to the one or more conductive elements and/or to receive a voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements.

Herein, it should be appreciated that "non-contact" coupling preferably refers to coupling that does not involve direct electrical ("ohmic") contact, preferably capacitive coupling. Thus, whilst the "non-contact" coupling between the or each electrode and the at least one conductive elements should not involve direct electrical contact between the or each electrode and the at least one conductive element, it would be possible, for example, for the at least one

conductive element to be protected by an electrically

insulative sheath and for the or each electrode to be in physical contact with the electrically insulative sheath. Herein, it should be appreciated that describing an electrode as being "adjacent" to one or more coupling elements preferably refers to the electrode being near to the one or more conductive elements, preferably with little or

substantially no electromagnetic shielding being between the electrode and the one or more conductive elements.

The voltage signal is preferably a differential voltage signal. A differential voltage signal can be understood as a voltage signal that includes a first voltage signal that is transmitted/received via a first signal path and a second voltage signal that is transmitted/received via a second signal path, the second voltage signal being complimentary (preferably opposite) to the first voltage signal. A

differential voltage signal can also be understood as a voltage signal that propagates between the first and second signal paths. These two different views of a differential voltage signal are essentially equivalent.

Although preferably a differential voltage signal, the voltage signal may instead be a single-ended voltage signal. A single-ended voltage can be viewed as including only one voltage signal that varies with respect to a fixed voltage, e.g. a local ground. This is different from a differential voltage, which includes two complimentary voltage signals.

A differential voltage signal is preferred because it has been found to propagate more reliably than a single-ended voltage signal.

UK patent application GB0905361.2, also by the present inventors, taught transmitting a voltage signal to the twisted pairs of a twisted pair cable using a pair of electrodes arranged to produce an electric field therebetween. A similar arrangement of electrodes was taught for the receiving of a voltage signal after it had propagated along a twisted pair cable. This arrangement of electrodes allowed a differential voltage signal to be transmitted to the twisted pair cable such that the signal propagated along the cable between at least two of the twisted pairs, and further allowed a

differential voltage signal to be received from the cable after the signal had propagated along the cable between at least two of the twisted pairs. The differential voltage signal was thought to result from an electric field produced between the pair of electrodes which caused a difference in voltage between the twisted pairs.

A similar electrode arrangement could be used with the present invention so as to produce a voltage signal that propagates between twisted pairs of a twisted pair cable. For example, the at least one electrode could include a pair of electrodes that are adjacent to (e.g. located on opposite sides of) a plurality of conductive elements of the coupling unit that are respectively electrically connected to the conductors of a twisted pair cable, the pair of electrodes being configured to: produce an electric field therebetween to transmit a (differential) voltage signal to the conductive elements by non-contact coupling with the conductive elements so that the voltage signal propagates along the twisted pair cable between at least two of the twisted pairs; and/or configured to receive a (differential) voltage signal from the plurality of conductive elements by non-contact coupling with the plurality of conductive elements after the voltage signal has propagated along the twisted pair cable between at least two of the twisted pairs.

However, this electrode arrangement was devised for a coupling unit that could potentially be clipped to the outside of an unshielded twisted pair cable. In the present case, the coupling unit includes a plurality of conductive elements configured to be electrically connected to the conductors of a twisted pair cable if the coupling unit is physically

connected to the twisted pair cable by the interface. This means that the electrode can be selectively placed adjacent to one or more of the conductive elements whilst e.g. being electromagnetically shielded from the othe rs . This permits many different electrode arrangements which may be preferred to the electrode arrangement described in UK patent

application GB0905361.2, also by the present inventors.

A preferred electrode arrangement, described below in more detail, involves the coupling unit having at least one first electrode adjacent to one or more first conductive elements of the coupling unit and at least one second

electrode adjacent to one or more second conductive elements of the coupling unit, these electrodes preferably being configured so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the first and second electrodes can transmit and/or receive a

differential voltage signal to and/or from the first and second conductive elements by non-contact coupling with the first and second conductive elements.

Another, simpler, electrode arrangement, also described below in more detail, involves the coupling unit having at least one electrode that is adjacent to one or more conductive elements of the coupling unit, the at least one electrode preferably being configured so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the at least one electrode can transmit and/or receive a single-ended voltage signal to and/or from the one or more conductive elements by non-contact coupling with the one or more conductive elements. Here a local ground may act as a return path for the single-ended voltage signal. Preferably, the local ground is provided by electromagnetic shielding of the twisted pair cable, since this may provide a stable ground by which the single-ended voltage signal can reliably

propagate .

Preferably, the coupling unit has: at least one first electrode that is adjacent to one or more first conductive elements of the coupling unit; and

at least one second electrode that is adjacent to one or more second conductive elements of the coupling unit.

This electrode arrangement is preferred because it allows a differential voltage signal to be transmitted and/or received to a twisted pair cable

Preferably, therefore, the at least one first electrode and the at least one second electrode are configured to transmit a differential voltage signal to the first and second conductive elements by non-contact coupling with the first and second conductive elements (preferably so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the differential voltage signal can

propagate along the twisted pair cable between the

conductor (s) of the twisted pair cable electrically connected to the one or more first conductive elements and the

conductor (s) of the twisted pair cable electrically connected to the one or more second conductive elements) and/or to receive a differential voltage signal from the first and second conductive elements by non-contact coupling with the first and second conductive elements (preferably so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the differential voltage signal can be received after it has propagated along the twisted pair cable between the conductor (s) of the twisted pair cable

electrically connected to the one or more first conductive elements and the conductor (s) of the twisted pair cable electrically connected to the one or more second conductive elements) .

Preferably, the coupling unit includes electromagnetic shielding arranged to shield the at least one first electrode from the at least one second electrode and/or electromagnetic shielding arranged to shield the one or more first conductive elements from the one or more second conductive elements. In this way, degradation of a differential voltage signal transmitted and/or received by the first and second electrodes can be reduced. The same portion of electromagnetic shielding may act as both the electromagnetic shielding arranged to shield the at least one first electrode from the at least one second electrode and the electromagnetic shielding arranged to shield the one or more first conductive elements from the one or more second conductive elements.

The coupling unit may include electrodes that are dedicated either to transmitting or receiving a voltage signal .

Accordingly, the coupling unit may have:

at least one first transmitter electrode that is adjacent to one or more first conductive elements of the coupling unit; and/or

at least one second transmitter electrode that is adjacent to one or more second conductive elements of the coupling unit;

wherein the at least one first transmitter electrode and the at least one second transmitter electrode are configured to transmit a differential voltage signal to the first and second conductive elements by non-contact coupling with the first and second conductive elements.

Similarly, the coupling unit may have:

at least one first receiver electrode that is adjacent to one or more first conductive elements of the coupling unit; and/or

at least one second receiver electrode that is adjacent to one or more second conductive elements of the coupling unit;

wherein the at least one first receiver electrode and the at least one second receiver electrode are configured to receive a differential voltage signal from the first and second conductive elements by non-contact coupling with the first and second conductive elements.

Preferably, the one or more first conductive elements adjacent to the at least one first transmitter electrode are the same as the one or more first conductive elements adjacent to the at least one first receiver electrode. Similarly, the one or more second conductive elements adjacent to the at least one second transmitter electrode are the same as the one or more second conductive elements adjacent to the at least one second receiver electrode, but this need not be the case.

If the coupling unit includes both transmitter and receiver electrodes, it preferably includes electromagnetic shielding arranged to shield the transmitter electrodes from the receiver electrodes, e.g. so as to inhibit a signal being transmitted directly therebetween.

For the avoidance of any doubt, whilst the coupling unit may includes both transmitter and receiver electrodes, it is also possible for the coupling unit to include only

transmitter electrodes or only receiver electrodes.

Although the at least one first electrode and the at least one second electrode may include electrodes that are dedicated either to transmitting or receiving a voltage signal, it is also possible for the same at least one first electrode and the same at least one second electrode to be configured to both transmit and receive a voltage signal.

Accordingly, the coupling unit may have:

at least one first transceiver electrode that is adjacent to the one or more first conductive elements of the coupling unit; and

at least one second transceiver electrode that is adjacent to the one or more second conductive elements of the coupling unit; wherein the at least one first transceiver electrode and the at least one second transceiver electrode are configured to transmit a differential vol ta ns .s i nn s l tn the* f i rs t a nd second conductive elements by non-contact coupling with the first and second conductive elements and to receive a

differential voltage signal from the first and second

conductive elements by non-contact coupling with the first and second conductive elements.

Configuring a transceiver electrode to both transmit and receive a voltage signal may be achieved, for example, using a directional coupler, which component is well known e.g. in the art of radio technology. Having transceiver electrodes configured to both transmit and receive a voltage signal may be advantageous in reducing the amount of space occupied by the electrodes, especially if there is little space for the electrodes in the coupling unit.

In some embodiments, the at least one electrode (which could be one solitary electrode) adjacent to the one or more conductive elements may be configured to transmit a single- ended voltage signal to the one or more conductive elements by non-contact coupling with the one or more conductive elements (preferably so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the single-ended voltage signal can propagate along the twisted pair cable via conductor (s) of the twisted pair cable

electrically connected to the one or more conductive elements) and/or to receive a single-ended voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements (preferably so that, if the coupling unit is physically connected to a twisted pair cable by the interface, the single-ended voltage signal can be received after it has propagated along the conductor (s) of the twisted pair cable electrically connected to the one or more conductive elements) . Here a local ground may act as a return path for the single-ended voltage signal. Preferably, the local ground is provided by electromagnetic shielding of the wis ed pai cable, since this may provide a stable ground by which the single-ended voltage signal can reliably propagate.

Preferably, to facilitate this, the coupling unit includes electromagnetic shielding configured to electrically connect to electromagnetic shielding of a shielded twisted pair cable, if the coupling unit is physically connected to the shielded twisted pair cable by an interface (e.g. a first or second interface) of the coupling unit.

The coupling unit may include one or more electrodes that are dedicated either to transmitting or receiving a single- ended voltage signal.

Accordingly, the coupling unit may have:

at least one transmitter electrode adjacent to one or more conductive elements, the at least one transmitter electrode being configured to transmit a single-ended voltage signal to the one or more conductive elements by non-contact coupling with the one or more conductive elements.

Similarly, the at least one electrode may have:

at least one receiver electrode adjacent to one or more conductive elements, the at least one receiver electrode being configured to receive a single-ended voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements.

If the coupling unit includes both at least one

transmitter and at least one receiver electrode, it preferably includes electromagnetic shielding arranged to shield the at least one transmitter electrode from the at least one receiver electrode, e.g. so as to inhibit a signal being transmitted directly therebetween. For the avoidance of any doubt, whilst the coupling unit may includes both transmitter and receiver electrodes, it is also possible for the coupling unit to include only one or more transmitter electrodes or one or more receiver

electrodes .

Although the at least one electrode may include

electrodes that are dedicated either to transmitting or receiving a voltage signal, it is also possible for the same at least one electrode to be configured to both transmit and receive a voltage signal. Accordingly, the coupling unit may have :

at least one transceiver electrode adjacent to one or more conductive elements of the coupling unit, the at least one transceiver electrode being configured to transmit a single-ended voltage signal to the one or more conductive elements by non-contact coupling with the one or more

conductive elements and to receive a single-ended voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements .

Configuring a transceiver electrode to both transmit and receive a voltage signal may be achieved, for example, using a directional coupler, which component is well known e.g. in the art of radio technology. Having transceiver electrode (s) configured to both transmit and receive a voltage signal may be advantageous in reducing the amount of space occupied by the electrodes, especially if there is little space for the electrodes in the coupling unit.

Preferably, the twisted pair cable is a shielded twisted pair cable, i.e. preferably the twisted pair cable includes electromagnetic shielding, e.g. as described above.

Preferably, the coupling unit includes electromagnetic shielding. As has already been discussed above,

electromagnetic shielding included in the coupling unit may include any one or more of: electromagnetic shielding arranged to shield at least one first electrode from at least one second electrode; electromagnetic shielding arranged to shield one or more first conductive elements from one or more second conductive elements; and/or electromagnetic shielding arranged to shield at least one transmitter electrode from at least one receiver electrode. Additionally, or alternatively, the coupling unit may include electromagnetic shielding arranged to shield the conductive elements from external

electromagnetic interference for the coupling unit and/or reduce crosstalk between coupling units. The electromagnetic shielding arranged to shield the conductive elements from external electromagnetic interference for the coupling unit and/or reduce crosstalk between coupling units may be

provided, for example, by a metal shell, e.g. which may be included in a housing of the coupling unit (e.g. as discussed below) .

If the coupling unit includes (any) electromagnetic shielding, the electromagnetic shielding of the coupling unit is preferably configured to electrically connect to

electromagnetic shielding of a shielded twisted pair cable, if the coupling unit is physically connected to the shielded twisted pair cable by an interface (e.g. a first or second interface) of the coupling unit. This may allow shielding of the coupling unit and twisted pair cable to provide a stable ground by which a voltage signal can reliably propagate.

If the coupling unit includes (any) electromagnetic shielding, the electromagnetic shielding of the coupling unit is preferably configured to electrically connect to a local ground, as electromagnetic shielding is generally more effective when connected to a ground.

Preferably, the interface of the coupling unit is one of two interfaces, preferably such that the conductive elements of the coupling unit can be used to electrically interconnect the conductors of two different twisted pair cables. This is preferable because it allows the interface of the coupling unit to be inserted into the middle of a channel including a plurality of twisted pair cables, rather than at the end of such a channel.

Accordingly, the coupling unit preferably includes:

a first interface for physically connecting the coupling unit to a first twisted pair cable;

a second interface for physically connecting the coupling unit to a second twisted pair cable;

wherein each conductive element of the coupling unit is configured to be electrically connected to a respective conductor of a first twisted pair cable and a respective conductor of a second twisted pair cable, if the coupling unit is physically connected to the first twisted pair cable by the first interface and to the second twisted pair cable by the second interface.

The first and/or second interface may be a plug (e.g. outwardly projecting or "male") interface or socket (e.g.

inwardly projecting or "female") interface, depending on design requirements. The first and/or second interface may conform to a standard for twisted pair cables, e.g. RJ45.

Preferably, the conductive elements of the coupling unit are grouped in one or more pairs, with the or each pair of conductive elements being configured to be electrically connected to both (e.g. forward and return) conductors of a respective twisted pair of a twisted pair cable, if the twisted pair cable is physically connected to the coupling unit by the interface. If the coupling unit includes a first interface and a second interface, then each pair of conductive elements is preferably configured to be electrically connected to both (e.g. forward and return) conductors of a respective twisted pair of a first twisted pair cable and both (e.g.

forward and return) conductors of a respective twisted pair of a second twisted pair cable, if the coupling unit is

physically connected to the first twisted pair cable by the f i rst, interface and to the second twisted pair cable by the second interface.

Preferably, the or each electrode of the coupling unit is adjacent to one or more pairs of conductive elements of the coupling unit. Thus, where "one or more ... conductive elements" are mentioned herein, this can be replaced by "one or more ... pairs of conductive elements". For example, "at least one electrode that is adjacent to one or more conductive elements" may be replaced by "at least one electrode that is adjacent to one or more pairs of conductive elements".

Similarly, "at least one first electrode that is adjacent to one or more first conductive elements" may be replaced by "at least one first electrode that is adjacent to one or more first pairs of conductive elements".

An advantage of having the or each electrode of the coupling unit adjacent to one or more pairs of conductive elements is that the or each pair of conductive elements can be electrically connected to both (e.g. forward and return) conductors of a respective twisted pair in a twisted pair cable, if the twisted pair cable is physically connected to the coupling unit by the interface. In this way, a voltage signal transmitted to a pair of conductive elements by an electrode of the coupling unit is able to propagate along both (e.g. forward and return) conductors of a twisted pair in the twisted pair cable. This is advantageous because a voltage signal that propagates along both (e.g. forward and return) conductors of a twisted pair will generally not interrupt any differential voltage signal (e.g. a data signal) propagating within the twisted pair (i.e. between the forward and return conductors of the twisted pair) .

Usually, a twisted pair cable includes a plurality of twisted pairs, in which case the coupling unit preferably includes a corresponding plurality of pairs of conductive elements. In this case, the coupling unit preferably includes electromagnetic shielding arranged to shield each pair of conductive elements from the other pair(s) of conductive elements. In this way, cross-coupling between the pairs of conductive elements can be reduced.

An aforementioned electrode may take the form of an electrode described, for example, in UK patent application number GB0905361.2, also by the present inventors.

For example, the or each electrode of the coupling unit may be provided in the form of a (respective) plate. The or each plate may be made of, for example, foil, e.g. copper foil.

Preferably, the or each plate has an area of 10 mm² (e.g. 3.16 mm by 3.16 mm) or larger. More preferably, the or each plate has an area 20 mm² (e.g. 4.47 mm by 4.47 mm) or larger, more preferably an area that is approximately equal to 20mm². The inventors have found that plates having such areas are large enough to transmit/receive a voltage signal to/from a twisted pair cable using the coupling unit such that the voltage signal propagates over useful distances, e.g. up to 100 metres.

The or each electrode (e.g. plate) may be constructed as described in UK patent application GB1018582.5 (a copy of which is annexed hereto) and/or as shown in Figs. 7 (a) -(c) below.

Accordingly, one or more electrodes of the coupling unit may be located (preferably printed) on one or more flexible circuit boards, e.g. of a suitable material such as polyimide. A ground plane may be located (preferably printed) on an opposite side of the or each flexible circuit board to the or each electrode. The ground plane may serve a useful electromagnetic screening/shielding role for the or each electrode and, as such, may form e.g. a part of

electromagnetic shielding of the coupling unit.

The coupling unit preferably has a housing or main body. The housing preferably houses at least some or all of the aforementioned components. For example, the housing may house the or each electrode. Similarly, the housing may contain the conductive elements. The housing preferably includes

mechanical elements, e.g. lugs, bevels, and/or retaining clips, for attaching the coupling unit to an external

apparatus, e.g. a patch panel. Preferably, the housing includes an electrically insulative (preferably plastic) inner body surrounded by an electrically conductive (preferably metal) shell. Here, the electrically conductive shell may provide electromagnetic shielding for the coupling unit, e.g. electromagnetic shielding arranged to shield the conductive elements from external electromagnetic interference and/or reduce crosstalk between coupling units.

Preferably, the coupling unit includes one or more connectors for connecting the at least one electrode to a voltage signal producing and/or processing apparatus.

For example, the coupling unit may include one or more connectors for conveying a voltage signal produced by a voltage signal producing and/or processing apparatus to at least one electrode of the coupling unit (e.g. at least one transmitter or transceiver electrode), e.g. so that the at least one electrode can transmit the voltage signal and/or for conveying a voltage signal received by at least one electrode of the coupling unit (e.g. at least one receiver or

transceiver electrode) to a voltage signal producing and/or processing apparatus, e.g. so that the voltage signal can be processed by the voltage signal producing and/or processing apparatus . The or each connector may, for example, take the form of a twisted pair cable (shielded or unshielded) , a coaxial cable or even a portion of a flexible circui board. In any case, the or each connector is preferably designed to ensure that any coupling between connectors (or between the conductors within the connectors) is small or negligible compared with the coupling between the at least one electrode and the one or more conductive elements.

One or more of the coupling units may be included in an apparatus having a voltage signal producing and/or processing apparatus configured:

to produce a voltage signal and to convey the voltage signal to at least one electrode of the coupling unit (e.g. at least one transmitter or transceiver electrode) , preferably such that the voltage signal is transmitted by the at least one electrode; and/or

to process a voltage signal conveyed from at least one electrode of the coupling unit (e.g. at least one receiver or transceiver electrode) , preferably after the voltage signal has been received by the at least one electrode.

The voltage signal producing and/or processing apparatus may, for example, include a voltage signal generator for producing the voltage signal and/or a separate voltage signal processor for processing the voltage signal. Components of the voltage signal producing and/or processing apparatus could be included in the coupling unit(s) rather than in the voltage signal generator and/or voltage signal processor. Preferably, however, the voltage signal producing and/or processing apparatus is configured to both produce and process a voltage signal, i.e. it is preferably a voltage signal producing and processing means. A voltage signal producing and processing means may, for example, be a vector network analyser ("VNA") , for example. The one or more coupling units are preferably connected to the voltage signal producing and/or processing apparatus, e.g. using one or more connectors of the or each coupling units, e.g. as described above.

The voltage signal producing and/or processing apparatus may be configured to convey a voltage signal to at least one electrode of the coupling unit via a connector, e.g. as described above. Similarly, the voltage signal producing and/or processing apparatus may be configured to convey a voltage signal from at least one electrode of the coupling unit via a connector, e.g. as described above.

Preferably, the voltage signal producing and/or

processing apparatus is configured to produce and/or process a differential voltage signal. For example, the voltage signal producing and/or processing apparatus may be configured to work with the electrode arrangement described above in which the coupling unit has at least one first electrode adjacent to one or more first conductive elements and at least one second electrode adjacent to one or more second conductive elements. Accordingly, the voltage signal producing and/or processing apparatus is preferably configured:

to produce a differential voltage signal and to convey the differential voltage signal to at least one first

electrode of the coupling unit (e.g. at least one first transmitter electrode or at least one first transceiver electrode) and at least one second electrode of the coupling unit (e.g. at least one second transmitter electrode or at least one second transceiver electrode) , preferably such that the differential voltage signal is transmitted by the at least one first electrode and the at least one second electrode; and/or

to process a differential voltage signal conveyed from at least one first electrode of the coupling unit (e.g. at least one first receiver electrode or at least one first transceiver electrode) and at least one second electrode of the coupling unit (e.g. at least one second receiver electrode or at least one second transceiver electrode) , preferably after the differential vo l ta ge signal has been received by the at least one first electrode and the at least one second electrode.

There are many different ways in which the voltage signal producing and/or processing apparatus could be configured to produce a differential voltage signal and convey it to at least one first electrode and at least one second electrode of the coupling unit. For example, the voltage signal producing and/or processing apparatus could include a voltage signal generator configured to produce a single-ended voltage signal and an electrical isolation means (e.g. a balun) configured to convert the single-ended voltage signal into a differential voltage signal before it is conveyed to the at least one first electrode and at least one second electrode of the coupling unit. A similar arrangement was taught in UK patent

application number GB0905361.2, also by the present inventors. By way of example, the aforementioned electrical isolation means could be included in the coupling unit, e.g. as taught by UK patent application number GB0905361.2.

Similarly, there are many different ways in which the voltage signal producing and/or processing apparatus could be configured to process a differential voltage signal conveyed from at least one first electrode and at least one second electrode of the coupling unit. For example, the voltage signal producing and/or processing apparatus could include an electrical isolation means configured to convert the

differential voltage signal into a single-ended voltage signal and a voltage signal processor configured to process the single-ended voltage signal. A similar arrangement was taught in UK patent application number GB0905361.2, also by the present inventors. By way of example, the aforementioned electrical isolation means could be included in the coupling unit, e.g. as taught by UK patent application number

GB0905361.2. In some embodiments, the voltage signal producing and/or processing apparatus is confi ured o produce and/or process a single-ended voltage signal. Accordingly, the voltage signal producing and/or processing apparatus may be configured:

to produce a single-ended voltage signal and to convey the single-ended voltage signal to at least one electrode of the coupling unit (e.g. at least one transmitter electrode or at least one transceiver electrode) , preferably such that the single-ended voltage signal is transmitted by the at least one electrode; and/or

to process a single-ended voltage signal conveyed from at least one electrode of the coupling unit (e.g. at least one receiver electrode or at least one transceiver electrode) , preferably after the single-ended voltage signal has been received by the at least one electrode.

Preferably, the coupling unit is for use in a network monitoring apparatus, e.g. an apparatus for monitoring a network, e.g. a telecommunications network such as a local area network, e.g. having a plurality of cables which

interconnect a plurality of network ports.

Accordingly, the first aspect of the invention may provide a network monitoring apparatus for monitoring a network, the network monitoring apparatus having:

one or more of the coupling units (e.g. twenty-four coupling units), the or each coupling unit being associated or configured to be associated with a respective network port in a network; and

a voltage signal producing and/or processing apparatus e.g. as described above, wherein the voltage signal producing and/or processing apparatus is configured to produce a voltage signal and to convey the voltage signal to at least one electrode of one or more of the coupling units and/or to process a voltage signal conveyed from at least one electrode of one or more of the coupling units. The network monitoring apparatus may be configured to monitor a network,- for exam l e? , by identifying one or more interconnections between network ports within a network (e.g. to produce a connection map of patch leads) and/or by

determining the physical condition or state of one or more channels within a network.

Herein, the terms "channel", "network channel", "cable line" and "network line" preferably refer to a cable or a plurality of cables connected together so as to be capable of carrying a signal. These terms may be used interchangeably. Preferably the one or more cables are twisted pair cables. The prefix "twisted pair" may be used with the terms "channel", "network channel", "cable line" and "network line" to indicate the presence of twisted pair cables within the channel.

Configuring the network monitoring apparatus to monitor a network by identifying one or more interconnections between network ports within a network may be achieved, for example, by the voltage signal producing and/or processing apparatus being configured to produce a voltage test signal and to convey the voltage test signal to (at least one electrode of) one of the coupling units, so that (the at least one electrode of) the coupling unit transmits the voltage test signal. If another coupling unit subsequently receives the voltage test signal, then an interconnection between the coupling unit that transmitted the voltage test signal and the coupling unit that received the voltage test signal can be identified, and therefore an interconnection between the network ports with which those coupling units are associated can be identified.

It should be appreciated that this is not the only way in which interconnections between network ports can be

identified. Other methods and apparatuses for identifying interconnections between coupling units are disclosed, for example, in UK patent applications GB0905361.2, GB1009184.1 and GB1018582.5, also by the present inventors.

Configuring the network monitoring apparatus to monitor a network by determining the physical condition or state of one or more channels within. the network may be achieved, for example, by the voltage signal producing and/or processing apparatus being configured to produce a voltage test signal and to convey the voltage test signal to (at least one electrode of) one of the coupling units, so that (the at least one electrode of) the coupling unit transmits the voltage test signal so that it propagates along a channel to which it is connected. If the same (or another) coupling unit subsequently receives the voltage test signal after it has propagated along the channel, then the received signal can be processed (e.g. analysed), e.g. by the voltage signal producing and/or processing apparatus, so as to determine the physical

condition or state of the channel using standard techniques, e.g. so as to ensure that data signals can propagate correctly within twisted pairs in the twisted pair cable or network channel. The voltage test signal might, for example, be a time domain reflectometry signal or a frequency domain

reflectometry signal. The standard techniques may be time domain reflectometry or frequency domain reflectometry .

It should be appreciated that this is not the only way in which the physical condition or state of one or more channels within a network can be determined. Other methods and

apparatuses for determining the physical condition or state of channels within a network are disclosed, for example, in UK patent applications GB0905361.2 and GB1018582.5, also by the present inventors .

The or each coupling unit may be configured to be installed in a patch panel, e.g. having suitable lugs, bevels and/or retaining clips for this purpose. Preferably, the or each coupling unit is installed in a patch panel. For the avoidance of any doubt, if there are a plurality of coupling units, the coupling units could be installed in different patch panels, i.e. the coupling units need not all be

installed in the same patch panel. The patch panel may form part of a local area network. Typically, a patch panel will have a front side having network ports into which shorter "patch" (twisted pair) cables are plugged and a back side into which longer, more permanent, "fixed" (twisted pair) cables are plugged.

Preferably, the or each coupling unit is configured so that its conductive elements become electrically connected to a twisted pair cable if the twisted pair cable is installed in the network port with which the coupling unit is associated.

The or each coupling unit could form an integral part of one or more patch panels. Accordingly, the monitoring

apparatus could include one or more patch panels, each patch panel including one or more coupling units that form an integral part of the patch panel. Components of the voltage signal producing and/or processing apparatus may also be included in one or more patch panels.

Alternatively the or each coupling unit may be configured to be retrofitted to an existing patch panel. The first aspect of the invention may provide a method of retrofitting a coupling unit as described herein to a patch panel.

Many different possible "retrofit" possibilities can be envisaged. For example, each coupling unit (which could have two socket interfaces, for example) could be configured to be connected to a respective network port at the back of a patch panel such that connecting a twisted pair cable to the network port is achieved by plugging the twisted pair cable into the coupling unit. As another example, each coupling unit could have a respective first interface (which could be a plug interface) and a respective second interface (which could be a socket interface) , wherein the first interface is configured to plug into a respective network port at the front of the patch panel such that connecting a twisted pair cable to the network port is achieved by plugging the twisted pair cable into a second interface of the coupling unit. Here, any above described connectors of the coupling unit could be led to a voltage signal producing and/or processing apparatus at the back of the patch panel. As another example, the coupling units and voltage signal producing and/or processing apparatus may be located in a common enclosure (e.g. twenty-four of them) with the whole assembly being configured to plug into the front of the patch panel.

The network monitoring apparatus could, for example, be an apparatus as disclosed in UK patent application GB1018582.5

(a copy of which is annexed hereto) . This patent application discloses various apparatuses for identifying interconnections in a network comprising a plurality of channels ("cable lines") and/or for determining the physical state of channels

("cable lines") in the network. Coupling units as described herein are preferably configured to be used as direct

replacements for the coupling units described in UK patent application GB1018582.5 (a copy of which is annexed hereto), e.g. serving substantially the same electrical function, preferably so as to permit the apparatuses described in that patent application to be used with shielded twisted pair cables .

The first aspect may also provide a kit of parts for forming a monitoring apparatus as described above. For example, the first aspect of the invention may provide:

a kit of parts for forming a network monitoring

apparatus, the kit of parts having:

one or more of the coupling units, the or each coupling unit being configured to be associated with a respective network port in a network; and a voltage signal producing and/or processing apparatus, wherein the voltage signal producing and/or processing apparatus is configured to produce a voltage signal and to convey the voltage signal to at least one electrode of one or more of the coupling units and/or to process a voltage signal conveyed from at least one electrode of one or more of the coupling units.

The first aspect may also provide a method of using a coupling unit described above to transmit and/or receive a voltage signal.

Accordingly, the first aspect of the invention may provide :

a method of using a coupling unit to transmit and/or receive a voltage signal, wherein the method includes:

physically connecting the coupling unit to a twisted pair cable using an interface of the coupling unit so that each of a plurality of conductive elements of the coupling unit become electrically connected to a respected conductor of the twisted pair cable; and

using at least one electrode that is adjacent to one or more conductive elements of the coupling unit to transmit a voltage signal to the one or more conductive elements and/or to receive a voltage signal from the one or more conductive elements by non-contact coupling with the one or more

conductive elements.

The method may include any method step implementing or corresponding to any apparatus feature described in connection with the first aspect of the invention.

A second aspect of the invention may provide a method of converting a coupling unit into a coupling unit according to the first aspect of the invention. Accordingly, the second aspect of the invention may provide :

a method of converting a coupling unit having*

a plurality of conductive elements, each conductive element being configured to be electrically connected to a respective conductor of a twisted pair cable, if the coupling unit is physically connected to the twisted pair cable by the interface;

wherein the method includes:

adding at least one electrode to the coupling unit that is adjacent to one or more conductive elements of the coupling unit, the at least one electrode being configured to transmit a voltage signal to the one or more conductive elements and/or to receive a voltage signal from the one or more conductive elements by non-contact coupling with the one or more

conductive elements.

The coupling unit (before conversion) may, for example, be a typical shielded socket, e.g. similar to that shown in Fig. 11.

The adding at least one electrode may include inserting the at least one electrode into a (respective) space in the coupling unit, e.g. between a plastic inner body and a metal shell of the coupling unit, e.g. between a plastic inner body and rear metal covers of a metal shell of the coupling unit.

The at least one electrode may be located (preferably printed) on a flexible circuit board.

The invention also includes any combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided. The apparatuses and methods described above may be used in conjunction with the apparatuses and methods taught in GB0905361.2, GB1009184.1 and GB1018582.5, also by the present inventors .

Herein, "approximately equal" preferably means equal to the extent that there is a percentage difference (or "error") of no more than 50%, 40%, 30%, 20%, 10%, 5%, 2% or 1%.

Examples of our proposals are discussed below, with reference to the accompanying drawings in which:

Fig. 1 shows a typical patch system organised into a server row, a cross-connect row and a network row.

Fig. 2 shows an example of a typical patch panel viewed from an edge of the casing of a patch panel.

Fig. 3 is an internal view of a coupling unit for use with a twisted pair cable, showing the internal components of the coupling unit.

Fig. 4 shows an example layout for the first and second transmitter electrodes of the coupling unit shown in Fig. 3.

Fig. 5 is an external view of the coupling unit shown in Fig. 3, showing the external form of the coupling unit.

Fig. 6 shows a possible deployment of the coupling unit shown in Fig. 3 in a network monitoring apparatus.

Figs. 7 (a) -(c) show the possible use of flexible circuit board for one or more electrodes of the coupling unit.

Fig. 8 is an internal view of another coupling unit for use with a twisted pair cable, showing the internal components of the coupling unit.

Fig. 9 shows an example layout for the transmitter electrode of the coupling unit shown in Fig. 8.

Fig. 10 is an external view of the coupling unit shown in Fig. 8, showing the external form of the coupling unit.

Fig. 11 shows the construction of a typical shielded socket for use with a shielded twisted pair cable.

Fig. 12 shows a test coupling unit that was constructed for experimental use in a test apparatus. Fig. 13 shows a test apparatus incorporating two of the test coupling units shown in Fig. 12.

Figs. 14(a) and (b) shows sample r sul s produced using the test apparatus of Fig. 13.

In general, the following discussion describes

embodiments of our proposals that have been devised in light of the above considerations and, in particular, a problem of how to allow voltage signals to be coupled into shielded twisted pair cables by non-contact (preferably capacitive) coupling .

In some embodiments, a coupling unit may be provided e.g. in the form of a monitoring insert which may contain

transmitter electrodes and/or receiver electrodes or

transceiver electrodes. The coupling unit could, for example, be slotted into a network, positioned for instance at a patch panel interface and could, for example, make use of standard plug and socket connections such as those based on the standard RJ45 connector. Preferably, the coupling unit is designed so that it does not compromise the data transfer properties of the network, e.g. so as to have little or no effect on the performance of the system. The electrodes are preferably positioned underneath electromagnetic shielding so as to couple with the conductors of shielded twisted pair cables in the network. The coupling unit may be used in a network monitoring apparatus and is preferably able to operate, in essence, in parallel with a host network.

The coupling unit could, for example, be used to exploit the apparatuses and methods disclosed in UK patent

applications GB0905361.2, GB1009184.1 and GB1018582.5, also by the present inventors.

The coupling unit can also be used in an installation procedure for a network monitoring apparatus such that the monitoring system can be easily fitted onto an operation host network. The functionality of software underpinning the network monitoring apparatus may, for example, be as disclosed in GB1Q18582.5 (a copy of which is annexed hereto⁾ .

Fig. 3 is an internal view of a coupling unit 100 for use with a twisted pair cable, showing the internal components of the coupling unit 100.

The coupling unit 100 is preferably for use in a network monitoring apparatus, e.g. as described below, and may therefore be referred to as a "monitoring insert".

The coupling unit 100 preferably has a first interface 102 for physically connecting the coupling unit 100 to a first twisted pair cable (not shown) and a second interface 104 for physically connecting the coupling unit to a second twisted pair cable (not shown) . Preferably, the first interface 102 is a plug interface and the second interface 104 is a socket interface. The plug and socket interfaces 102, 104 may conform to a standard for twisted pair cables, e.g. RJ45, e.g. so that the coupling unit can be fitted at a node on a local area network, e.g. at a patch panel, e.g. as shown in Fig. 6 which is described below.

In Fig. 3, the coupling unit 100 is shown with the first (plug) interface 102 at one end and the second (socket) interface 104 at the other, but other arrangements are possible .

The coupling unit preferably has a housing 110, e.g.

including a plastic inner body surrounded by a metal shell. The housing 110 preferably houses components of the coupling unit, e.g. the electrodes and conductive elements described below. The housing 110 preferably includes mechanical

elements, e.g. lugs, bevels, and/or retaining clips (not shown) , for attaching the coupling unit 100 to a patch panel, e.g. as a physical replacement to an existing RJ-45 type socket .

The coupling unit 100 preferably has a plurality of (in this example eight) conductive elements 120, preferably grouped in pairs 120a, 120b, 120c, 120d. Each pair of

conductive elements 120a, 120b, 120c, 120d of the coupling unit is preferably configured to be electrically connected to both (e.g. forward and return) conductors of a respective twisted pair of a first twisted pair cable and to both (e.g. forward and return) conductors of a respective twisted pair of a second twisted pair cable if the coupling unit is physically connected to the first twisted pair cable by the first (plug) interface 102 and to the second twisted pair cable by the second (socket) interface 104. This may, for example, be achieved by respective electrical contacts 122, 124 being suitably positioned at either end of each conductive element 120. Fig. 3 shows the pairs of conductive elements 120a, 120b, 120c, 120d as being connected point to point between

respective electrical contacts 122, 124 on the first (plug) and second (socket) interfaces 102, 104.

The coupling unit 100 is preferably designed to ensure that the integrity of transmission of data within the pairs of conductive elements 120a, 120b, 120c, 120d is not compromised. For instance the characteristic impedance of channels (or "data lines") within twisted pair cables to which the coupling unit may be physically connected, typically 100 Ohm, would preferably be maintained through the coupling unit 100.

The coupling unit 100 preferably has a first transmitter electrode 130a that is adjacent to the first pair of

conductive elements 120a of the coupling unit and a second transmitter electrode 130b that is adjacent to the second pair of conductive elements 120b of the coupling unit 100.

Preferably, the first transmitter electrode 130a and the second transmitter electrode 130b are configured to transmit a differential voltage signal to the first and second pairs of conductive elements 120a, 120b by non-contact (capacitive) coupling wi h the first and second pairs of conductive elements 120a, 120b, preferably so that, if the coupling unit 100 is physically connected to a twisted pair cable by the first or second interface 102, 104, the differential voltage signal propagates along the twisted pair cable between the twisted pair of the twisted pair cable electrically connected to the first pair of conductive elements 120a and the twisted pair of the twisted pair cable electrically connected to the second pair of conductive elements 120b.

The coupling unit 100 preferably has a first receiver electrode 132a that is adjacent to the first pair of

conductive elements 120a of the coupling unit and a second receiver electrode 132b that is adjacent to the second pair of conductive elements 120b of the coupling unit 100. Preferably, the first receiver electrode 132a and the second receiver electrode 132b are configured to receive a differential voltage signal from the first and second pairs of conductive elements 120a, 120b by non-contact (capacitive) coupling with the first and second pairs of conductive elements 120a, 120b, preferably so that, if the coupling unit 100 is physically connected to a twisted pair cable by the first or second interface 102, 104, the differential voltage signal is received after it has propagated along the twisted pair cable between the twisted pair of the twisted pair cable

electrically connected to the first pair of conductive elements 120a and the twisted pair of the twisted pair cable electrically connected to the second pair of conductive elements 120b.

Each electrode 130a, 130b, 132a, 132b of the coupling unit 100 may be provided in the form of a respective plate. Each plate may be made of, for example, foil, e.g. copper foil. Preferably, each plate has an area of 10mm² or larger. More preferably, each plate has an area 20mm² or larger, more preferably an area that is approximately equal to 20mm².

The coupling unit 100 shown in Fig. 3 may be referred to as a "transceiver" coupling unit, as it is preferably

configured to both transmit a voltage signal to, and receive a voltage signal from, a twisted pair cable in the manner described above. However, "transmitter" coupling units

(configured only to transmit a voltage signal to a twisted pair cable, e.g. having only transmitter electrodes 130a, 130b) and "receiver" coupling units (configured only to receive a voltage signal from a twisted pair cable, e.g.

having only receiver electrodes 132a, 132b) are also

envisaged .

The coupling unit 100 preferably includes electromagnetic shielding 140a, 140b, preferably of a conductive material. In particular, the coupling unit preferably includes

electromagnetic shielding 140a arranged to shield the first electrodes 130a, 132a from the second electrodes 130b, 132b, electromagnetic shielding 140a arranged to shield the first pair of conductive elements 120a from the second pair of conductive elements 120b (more preferably arranged to shield each pair of conductive elements from the other pairs of conductive elements) , and/or electromagnetic shielding 140b arranged to shield the transmitter electrodes 130a, 130b from the receiver electrodes 132a, 132b.

The electromagnetic shielding 140a, 140b is preferably configured to electrically connect to electromagnetic

shielding of a shielded twisted pair cable (not shown) , if the coupling unit 100 is physically connected to the shielded twisted pair cable by the first or second interface 102, 104.

It should be appreciated that Fig. 3 is diagrammatical and has the purpose of illustrating what internal components are included in the coupling unit 100. Fig. 3 does not necessarily show the actual layout of the internal components of the coupling unit 100.

Fig. 4 shows an example layout for the first and second transmitter electrodes 130a, 130b of the coupling unit 100 shown in Fig. 3.

The symbols "+" and "-" shown in the conductive elements 120 in Fig. 4 respectively indicate "forward" and "return" conductive elements 120, e.g. which are respectively to be connected to the forward and return conductors of a twisted pair in a twisted pair cable.

As shown in Fig. 4, a first voltage signal +V of a differential voltage signal is conveyed to the first

transmitter electrode 130a, with a second, complimentary, voltage signal -V of the differential voltage signal being conveyed to the second transmitter electrode 130b. Here, the electromagnetic shielding 140a, 140b of the coupling unit is connected to a local ground and may be viewed as being at 0V relative to the differential voltage signal. In use, an electric field is produced between the first transmitter electrode 130a and the first pair of conductive elements 120a, so as to couple the first voltage signal +V of the

differential voltage signal to the first pair of conductive elements 120a. Similarly, in use, an electric field is produced between the second transmitter electrode 130b and the second pair of conductive elements 120b, so as to couple the second voltage signal -V of the differential voltage signal to the second pair of conductive elements 120b. In this way, the first transmitter electrode 130a and the second transmitter electrode 130b are able to transmit a differential voltage signal to the first and second pairs of conductive elements 120a, 120b by non-contact (capacitive) coupling with the first and second pairs of conductive elements 120a, 120b, so that, if the coupling unit 100 is physically connected to a twisted pair cable by the first or second interface 102, 104, the differential voltage signal can propagate along the twisted pair cable between the twisted pair of the twisted pair cable electrically connected to the first pair of conductive elements 120a and the twisted pair of the twisted pair cable electrically connected to the second pair of conductive elements 120b. Here, electromagnetic shielding of the twisted pair cable may act as a return path for the first and second voltage signals of the differential voltage signal (these two voltage signals will generally cancel each other out on the return path) .

The same layout of electrodes can also be used for the first and second receiver electrodes 132a, 132b, with the first receiver electrode 132a replacing the first transmitter electrode 130a and with the second receiver electrode 132b replacing the second transmitter electrode 130b. In use, a first voltage signal +V of a differential voltage signal can be received from the first pair of conductive elements 120a by the first receiver electrode 132a as a result of an electric field produced between the first pair of conductive elements 120a and the first receiver electrode 132a. Similarly, in use, a second voltage signal -V of a differential voltage signal can be received from the second pair of conductive elements 120b by the second receiver electrode 132b as a result of an electric field produced between the second pair of conductive elements 120b and the second receiver electrode 132b. In this way, the first receiver electrode and the second receiver electrode are able to receive a differential voltage signal from the first and second pairs of conductive elements 120a, 120b by non-contact (capacitive) coupling with the first and second pairs of conductive elements 120a, 120b, so that, if the coupling unit is physically connected to a twisted pair cable by the first or second interface, the differential voltage signal can be received after it has propagated along the twisted pair cable between the twisted pair of the twisted pair cable electrically connected to the first pair of conductive elements 120a and the twisted pair of the twisted pair cable electrically connected to the second pair of conductive elements 120b.

Fig. 5 is an external view of the coupling unit 100 shown in Fig. 3, showing the external form of the coupling unit 100.

The coupling unit 100 preferably includes a first connector 150 for conveying a differential voltage signal produced by a voltage signal producing and/or processing apparatus (not shown) to the first and second transmitter electrodes 130a, 130b of the coupling unit 100. The coupling unit 100 preferably includes a second connector 152 for conveying a differential voltage signal received by the first and second receiver electrodes 132a, 132b of the coupling unit 100 to a voltage signal producing and/or processing apparatus. The connectors 150, 152 could also be for coupling the shielding of the coupling unit 200 to a local ground.

Each connector may 150, 152, for example, take the form of a twisted pair cable (shielded or unshielded) or a coaxial cable. In any case, the connectors are preferably designed to ensure that any coupling between the connectors (or between the conductors within the connectors) is small or negligible compared with the coupling between the electrodes 130a, 130b, 132a, 132b and the first and second pairs of conductive elements 120a, 120b.

Fig. 6 shows a possible deployment of the coupling unit 100 shown in Fig. 3 in a network monitoring apparatus 160.

The network monitoring apparatus 160 preferably has one or more of the coupling units 100, the or each coupling unit 100 preferably being associated or configured to be associated with a respective network port in a network, and a voltage signal producing and/or processing apparatus 170, wherein the voltage signal producing and/or processing apparatus 170 is preferably configured to produce a differential voltage signal and to convey the differential voltage signal to the first and second transmitter electrodes of one or more of the coupling units 100 and/or to process a voltage signal conveyed from the first and second receiver electrodes of one or more of the coupling units 100.

For clarity, only one coupling unit 100a is illustrated in Fig. 6, but it should be apparent that many other coupling units 100 are preferably included.

Preferably, the coupling units 100 are installed in (e.g. a respective channel of) a patch panel 180 of a local area network with each coupling unit 100 being associated with a respective network port of the patch panel 180. Preferably, each coupling unit 100 is configured so that its conductive elements 120 become electrically connected to a twisted pair cable if the twisted pair cable is installed in the network port with which the coupling unit 100 is associated.

The coupling unit 100a illustrated in Fig. 6 is shown as being installed internally within the patch panel 180, connected to (and located between) a socket 182a of a fixed cable 182 within the patch panel 180 and a plug 184a of an external patch cable 184, with its first and second connectors 150, 152 being connected to the voltage signal producing and/or processing apparatus 170. Naturally, the patch cable 184 may or may not be present depending on the usage of the particular network port on the patch panel.

Of course, alternative variants of the arrangement shown in Fig. 6 can be envisaged.

For example, the one or more coupling units 100 could form an integral part of one or more patch panels.

Accordingly, the network monitoring apparatus 160 could include one or more patch panels, each patch panel including one or more coupling units 100 that form an integral part of the patch panel. Components of the voltage signal producing and/or processing apparatus 170 may also be included in one or more patch panels.

As another example, the one or more coupling units 100 could be configured to fit to the front of the patch panel 180, rather than internally within the patch panel.

As another example, the plurality of coupling units may be configured to be retrofitted to existing patch panels. Many different possible "retrofit" possibilities can be envisaged and some such possibilities have already been discussed above.

Preferably, the voltage signal producing and/or

processing apparatus 170 is configured to produce a

differential voltage signal and to convey the differential voltage signal to the first transmitter electrode 130a and the second transmitter electrode 130b of a coupling unit 100.

The voltage signal producing and/or processing apparatus 170 could, for example, be configured to produce a

differential voltage signal and convey it to the first and second transmitter electrodes 130a, 130b of a coupling unit 100 using an arrangement similar to that disclosed in UK patent applications GB0905361.2, also by the present

inventors, e.g. using a voltage signal generator configured to produce a single-ended voltage signal and an electrical isolation means (e.g. a balun) configured to convert the single-ended voltage signal into a differential voltage signal before it is conveyed to the first and second transmitter electrodes 130a, 130b.

Preferably, the voltage signal producing and/or .

processing apparatus 170 is configured to process a

differential voltage signal conveyed from the first receiver electrode 132a and the second receiver electrode 132b of a coupling unit 100. The voltage signal producing and/or processing apparatus 170 could,- for example, be configured to process a

differential voltage signal conveyed from the first receiver electrode 132a and the second receiver electrode 132b of a coupling unit 100 using an arrangement similar to that disclosed in UK patent applications GB0905361.2, also by the present inventors, e.g. using an electrical isolation means to convert the differential voltage signal into a single-ended voltage signal and a voltage signal processor configured to process the single-ended voltage signal.

The network monitoring apparatus 160 may be configured to monitor the network, for example, by identifying one or more interconnections between network ports within a network (e.g. to produce a connection map of path leads) and/or by

determining the physical condition or state of one or more channels within the network.

Configuring the network monitoring apparatus 160 to monitor a network by identifying one or more interconnections between network ports within a network may be achieved, for example, by the voltage signal producing and/or processing apparatus 170 being configured to produce a voltage test signal and to convey the voltage test signal to the first and second transmitter electrodes 130a, 130b of one of the coupling units 100, so that the first and second transmitter electrodes 130a, 130b of the coupling unit 100 transmit the voltage test signal. If another coupling unit 100 subsequently receives the voltage test signal, then an interconnection between the coupling unit 100 that transmitted the voltage test signal and the coupling unit 100 that received the voltage test signal can be identified, and therefore an interconnection between the network ports with which those coupling units 100 are associated can be identified. It should be appreciated that this is not the only way in which interconnections between network ports can be

Configuring the network monitoring apparatus 160 to monitor the network by determining the physical condition or state of one or more channels within the network may be achieved, for example, by the voltage signal producing and/or processing apparatus 170 being configured to produce a voltage test signal and to convey the voltage test signal to the first and second transmitter electrodes 130a, 130b of one of the coupling units 100, so that the first and second transmitter electrodes 130a, 130b of the coupling unit 100 transmits the voltage test signal so that it propagates along a channel to which it is connected. If the same (or another) coupling unit 100 subsequently receives the voltage test signal after it has propagated along the channel, then the received signal can be processed (e.g. analysed), e.g. by the voltage signal

producing and/or processing apparatus 170, so as to determine the physical condition or state of the channel using standard techniques, e.g. so as to ensure that data signals can propagate correctly within twisted pairs in the twisted pair cable or network channel. The voltage test signal might, for example, be a time domain reflectometry signal or a frequency domain reflectometry signal. The standard techniques may be time domain reflectometry or frequency domain reflectometry .

apparatuses for determining the physical condition or state of channels within a network are disclosed, for example, in UK patent applications GB0905361.2 and GB1018582.5, also by the present inventors. The network monitoring apparatus 160 could, for example, be an apparatus as disclosed in UK patent application

GB1018582.5 (a copy of which is annexed hereto). This patent application discloses various apparatuses for identifying interconnections in a network comprising a plurality of channels ("cable lines") and/or for determining the physical state of channels ("cable lines") in the network. Coupling units 100 as described herein are preferably configured to be used as direct replacements for the coupling units described in UK patent application GB1018582.5 (a copy of which is annexed hereto), e.g. serving substantially the same

electrical function, preferably so as to permit the

apparatuses described in that patent application to be used with shielded twisted pair cables.

Fig. 7(a) is a perspective view. Fig. 7(b) show the view from the electrode ("plate") side and Fig. 7(c) is an

illustration of the view from the ground plane side.

As shown in Figs. 7 (a) -(c), a pair of electrodes (e.g. plates) of the coupling unit 100, e.g. the transmitter electrodes 130a, 130b or the receiver electrodes 132a, 132b, may be located (preferably printed) on a flexible circuit board 134, e.g. of a suitable material such as polyimide. A ground plane 136 may be located (preferably printed) on an opposite side of the flexible circuit board 134 to the electrodes 130a/132a, 130b/132b. The ground plane 136 may serve a useful electromagnetic screening/shielding role for the electrodes 130a/132a, 130b/132b and, if the coupling unit has electromagnetic shielding 140a, 140b, the ground plane may form part of the electromagnetic shielding 140a, 140b. Figs. 7 (a) -(c) thereby highlights the use of flexible printed board (PCB) material such as polyimide or similar substrate material as a convenient and inexpensive means of realising a pair of transmitter electrodes 130a, 130b or receiver electrodes 132a, 132b for the coupling unit 100.

In summary, the electrodes of the coupling unit shown in Fig. 3 are able to couple capacitively to selected channels (or "data lines") such that voltage test signals (or

"monitoring signals") can be applied to the network in a similar manner to that described in UK patent application GB0905361.2, also by the present inventors. Capacitive coupling may be achieved through the dielectric insulation surrounding the data lines. In addition, internal shielding or screening is typically included to reduce direct coupling between the transmitter and receiver electrodes (or "plates") and unwanted coupling between the electrodes (or "plates") and non-selected data lines depending on the routing of the conductive elements (or "connecting tracks") to the

transmitter and receiver electrodes (or "plates") .

Alternative embodiments of the coupling unit are envisaged.

For example, a pair of electrodes forming a small value coupling capacitor (e.g. having a capacitance of the order of 1 pF) could be used (instead of individual electrodes) to achieve the non-contact (capacitive) coupling function previously achieved by individual electrodes.

As another example, instead of first and second

transmitter electrodes 130a, 130b and first and second receiver electrodes 132a, 132b, the coupling unit 100 may instead include first and second transceiver electrodes, wherein first transceiver electrode and the second transceiver electrode are configured to transmit a differential voltage signal to the first and second conductive elements 120a, 120b by non-contact coupling with the first and second conductive elements 120a, 120b and to receive a differential voltage signal from the first and second conductive elements 120a, 120b by non-contact coupling with the first and second conductive elements 120a, 120b. Configuring a transceiver electrode to both transmit and receive a voltage signal may be achieved, for example, using a directional coupler, which component is well known e.g. in the art of radio technology.

As another example, instead of the electrode arrangement shown in Fig. 5 for transmitting and/or receiving a

differential voltage signal, an electrode arrangement for transmitting and/or receiving a single-ended voltage signal is also possible, e.g. with a single electrode being used to transmit and/or receive a single-ended voltage signal to conductive elements (data lines) . Here, shielding of a twisted pair cable may act as a return path for the single-ended voltage signal. A coupling unit including such an electrode arrangement is shown in Fig. 8 and discussed below.

Fig. 8 is an internal view of another coupling unit 200 for use with a twisted pair cable, showing the internal components of the coupling unit 200.

The coupling unit 200 shown in Fig. 8 has many features which are the same as the coupling unit 100 shown in Fig. 3. Alike features have been given corresponding reference numerals and need not be described in further detail.

The coupling unit 200 preferably has a transmitter electrode 230 (which may be a solitary transmitter electrode) that is adjacent to the first pair of conductive elements 220a of the coupling unit, the transmitter electrode 230 being configured to transmit a single-ended voltage signal to the first pair of conductive elements 220a by non-contact

(capacitive) coupling with the pair of conductive elements 220a, preferably so that, if the coupling unit 200 is physically connected to a twisted pair cable by the first or second interface 202, 204, the single-ended voltage signal propagates along the twisted pair cable via the twisted pair of the twisted pair cable electrically connected to the first pair of conductive elements 220a. Here, electromagnetic shielding of the twisted pair cable may act as a return path for the single-ended voltage signal.

The coupling unit preferably has a receiver electrode 232 (which may be a solitary receiver electrode) that is adjacent to the first pair of conductive elements 220a, the receiver electrode 232 being configured to receive a single-ended voltage signal from the first pair of conductive elements 220a by non-contact (capacitive) coupling with the first pair of conductive elements 220a, preferably so that, if the coupling unit 200 is physically connected to a twisted pair cable by the interface, the single-ended voltage signal is received after it has propagated along the twisted pair cable via the twisted pair of the twisted pair cable electrically connected to the first pair of conductive elements 220a.

The coupling unit 200 may have electromagnetic shielding 240a, 240b similar to that described in connection with the coupling unit 100 shown in Fig. 3.

Fig. 9 shows an example layout for the transmitter electrode 230 of the coupling unit 200 shown in Fig. 8.

As shown in Fig. 9, a single-ended voltage signal V is conveyed to the transmitter electrode 230. Here, the

electromagnetic shielding 240a, 240b of the coupling unit 200 is preferably connected to a local ground and may be viewed as being at 0V relative to the single-ended voltage signal. In use, an electric field is produced between the transmitter electrode 230 and the first pair of conductive elements 220a, so as to couple the single-ended voltage signal to the first pair of conductive elements 220a. The same electrode layout can also be used for the receiver electrode 232, i.e. with the receiver electrode 230 taking the place of the transmitter electrode 230. In use, a single-ended voltage signal V can be received from the first pair of conductive elements 220a as a result of an electric field produced between the pair of conductive elements 220a and the receiver electrode 232.

Fig. 10 is an external view of the coupling unit 200 shown in Fig. 8, showing the external form of the coupling unit 200.

As shown in Fig. 10, the coupling unit 200 preferably includes a connector 250 for conveying a single-ended voltage signal produced by a voltage signal producing and/or

processing apparatus to the transmitter electrode 230 of the coupling unit 200, and for conveying a single-ended voltage signal received by the receiver electrode 232 of the coupling unit 200 to a voltage signal producing and/or processing apparatus. The connector 250 could also be for coupling the shielding of the coupling unit 200 to a local ground.

The connector 250 may, for example, take the form of a twisted pair cable (shielded or unshielded) or a coaxial cable .

The coupling unit shown in Fig. 8 may be deployed in a similar fashion to that shown in Fig. 3, except that a single- ended voltage signal, rather than a differential voltage signal may be produced and/or processed by a voltage signal producing and/or processing apparatus.

Fig. 11 shows the construction of a typical shielded (e.g. RJ45-type) socket 300 for use with a shielded twisted pair cable, e.g. for use with a STP or F/UTP cable. A housing of the shielded socket 300 includes a plastic inner body 310 surrounded by a metal shell 320. The metal shell 3?0prr>vi dps si ectromagneti r. shielding for the shielded socket 300. A cable 330 is connected to the shielded socket using insulated displacement connection (IDC) type terminals 312 contained in the plastic inner body 310. The IDC terminals are typically enclosed by rear metal covers 320a, 320b of the metal shell 320 which are removable to allow the cable 330 to be fitted and yet maintain screening integrity and clamp the cable 330 in place once the shielded socket 300 is assembled. On some shielded sockets there are spaces between the plastic inner body 310 containing the IDC terminals 312 and the rear metal covers 320a, 320b of the metal shell 320. These spaces may be able to accommodate an electrode, e.g. printed on a flexible circuit board.

Accordingly, a conventional coupling unit, e.g. a shielded socket 300 as shown in Fig. 11, could be converted into a coupling unit according to the invention, e.g. by inserting at least one electrode, e.g. printed on a flexible circuit board, into a (respective) space between a plastic inner body 310 containing IDC terminals 312 and rear metal covers 320a, 320b of a metal shell 320.

Example

Fig. 12 shows a test coupling unit 400 that was

constructed for experimental use in a test apparatus described below.

The test coupling unit 400 was made by converting a typical shielded socket 404 similar to that shown in Fig. 11, and a typical shielded plug 402, the shielded socket 404 and shielded plug 402 being joined to each other by a short length of shielded twisted pair cable 406. Here, the shielded plug 402 acts as a first interface of the test coupling unit 400 and the shielded socket 404 acts as a second interface of the test coupling unit 400. Two electrodes, made using a flexible PCB similar to that shown in Fig. 7, were added by inserting the electrodes into respective spaces between an inner plastic body and a metal shell in the shielded socket, such that a first electrode was adjacent to a first pair of conductive elements within the socket and a second electrode was adjacent to a second pair of conductive elements within the socket. The test unit also includes a connector 450 (twisted pair cable) for connecting the two electrodes of the coupling unit to a voltage signal producing and/or processing apparatus.

Fig. 13 shows a test apparatus 460 incorporating two of the test coupling units 400 shown in Fig. 12.

In the test apparatus 460, two of the test coupling units 400 described with reference to Fig. 12 are connected in line, with a first test coupling unit 400a acting as a transmitter coupling unit and a second test coupling unit 400b acting as a receiver. The connectors 450a, 450b of the test coupling units 400a, 400b are connected to a voltage signal producing and/or processing apparatus 470 which in this case includes a vector network analyser (VNA) with a frequency range from 1 MHz to 500 MHz with matching baluns for single-ended to differential voltage signal conversion.

It should be appreciated that although Fig. 13 shows the voltage signal producing and/or processing apparatus 470 as a vector network analyser for experimental purposes, the test coupling units 400a, 400b could instead be connected to the voltage signal producing and/or processing apparatus of a network monitoring apparatus, e.g. configured to identify interconnections between network ports within a network (e.g. to produce a connection map of path leads) and/or to determine the physical condition or state of channels within the network, e.g. an apparatus as described in GB1018582.5 (a copy of which is annexed hereto) . The test apparatus 460 shows the transmitter test coupling unit 400a as being connected to an unt rminated 2 m STP cable 480a and the receiver test coupling unit 400b as being connected (by a conventional coupling unit 481 such as that shown in Fig. 11) to a 24 m STP cable 480b. As shown in Fig. 12, an extra 2 m STP fly lead 482 is connected to a distal end of the 24 m STP cable 480b.

Figs. 14(a) and (b) shows sample results produced using the test apparatus of Fig. 13.

The sample results shown in Figs. 14(a) and (b) were both produced by performing time domain reflectometry using the vector network analyser 470 to produce and process

differential voltage signals and convey those signals to and from the electrodes of the transmitter test coupling unit 400a and the receiver coupling unit 400b respectively.

Fig. 14(a) shows the results obtained when the 24 m STP cable 480a was left unconnected at its distal end, i.e. with the extra 2 m STP fly lead 482 removed. Note that Fig. 14(a) incorrectly shows the length of the 24 m STP cable 480a as 27 m due to signal delays in the vector network analyser 470, which could be removed by calibration of the test apparatus 460 and are not of significance here.

Fig 14 (b) shows the results obtained when the extra 2 m STP fly lead 482 was connected to the distal end of the 24 m STP cable 480a. Fig. 14(b) therefore shows the change caused by the addition of the extra 2 m fly lead 482 and indicates that the overall length of the channel has increased by 2 m on the trace.

/ These sample results show the ability of the test coupling units 400a, 400b to transmit and receive a

differential voltage signal and further demonstrate that the ability of the test coupling units 400a, 400b to be used as part of a network monitoring apparatus performing

When used in this specification and claims, the terms "comprises", "comprising", "including", "has" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or integers.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may,

separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many

equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure, without departing from the broad concepts disclosed. It is therefore intended that the scope of the patent granted hereon be limited only by the appended claims, as interpreted with reference to the description and drawings, and not by

limitation of the embodiments described herein.

ANNEX - COPY OF UK PATENT APPLICATION GB1018582 . 5

In this copy of UK patent application GB1018582.5. the figures have been renumbered to avoid conflict with the other figures in this patent application and references to published patent applications have been updated.

APPARATUS FOR IDENTIFYING INTERCONNECTIONS AND/OR DETERMINING THE PHYSICAL STATE OF CABLE LINES IN A NETWORK AND ASSOCIATED

COMPONENTS

This invention relates to developments concerning apparatuses for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state (i.e. condition) of cable lines in the network. In some embodiments, this invention may relate to developments concerning apparatuses for both identifying interconnections in a network comprising a plurality of cable lines and for determining the physical state of cable lines in the network. The network may be a local area network, for example .

In some embodiments, test signals are transmitted and received for network inspection purposes. In some embodiments, the test signals are coupled into out from the cable lines of the network using non-contacting coupling units. Analysis of test signals coupled out from the cable lines can used to identify interconnections in the network, e.g. so as to allow a connection map of patch leads to be produced. Analysis of the test signals can also be used be used to determine the physical state (i.e. condition) of cable lines in the network, e.g. so as to ensure that network data traffic can propagate correctly .

Cables which include a plurality of twisted pairs, referred to as "twisted pair cables" herein, are well known. Such cables are commonly used for telecommunications purposes, e.g. computer networking and telephone systems. In the field of telecommunications, twisted pair cables are usually provided without shielding, as unshielded twisted ai (UTP) cables. However, shielded twisted pair (STP) cables are also known .

In this context, a "twisted pair" is a pair of

conductors, usually a forward conductor and a return conductor of a single circuit, which have been twisted together. The conductors are usually twisted together for the purposes of cancelling out electromagnetic interference from external sources and to minimise crosstalk between neighbouring twisted pairs within a cable comprising a plurality of twisted pairs. In this way, each twisted pair provides a reliable respective communication channel for a signal, usually a differential voltage signal, to be conveyed within the twisted pair. Common forms of unshielded twisted pair (UTP) cables are category 5 and category 6 UTP cables which include eight conductors twisted together in pairs to form four twisted pairs.

The design and construction of twisted pair cables is carefully controlled by manufacturers to reduce noise due to electromagnetic interference and to reduce crosstalk between the twisted pairs within the cables. To this end, each twisted pair in a twisted pair cable normally has a different twist rate (i.e. number of twists per unit length along the cable) from that of the other twisted pairs in the twisted pair cable. It is also usual for the twisted pairs to be twisted around each other within the cable. Fillets or spacers may be used to separate physically the twisted pairs.

Networks including ports interconnected by a plurality of cables, such as local area networks (LANs), are also well known. LANs are typically used to enable equipment such as computers, telephones, printers and the like to communicate with each other and with remote locations via an external service provider. LANs typically utilise twisted pair network cables, usually in the form of UTP cables.

The cables used in LANs are typically connected to dedicated service ports throughout one or more buildings. The cables from the dedicated service ports can extend through the walls, floor and/or ceilings of the building to a

communications hub, typically a communications room containing a number of network cabinets. The cables from wall and floor sockets within the building and from an external service provider are also usually terminated within the communications room.

A "patch system" may be used to interconnect various ports of the LAN within the network cabinets. In a patch system, all cable lines in the LAN can be terminated within the network cabinets in an organized manner. The terminations of the cable lines in the network are provided by the

structure of the network cabinets, which are typically organised in a rack system. The racks contain "patch panels", which themselves utilise sets of ports, typically RJ-45 type connector ports, at which the cable lines terminate.

Each of the ports in each patch panel is hard wired to one of the cable lines in the LAN. Accordingly, each cable line is terminated on a patch panel in an organized manner. In small patch systems, all cable lines in the LAN may terminate on the patch panels of the same rack. In larger patch systems, multiple racks are used, wherein different cable lines terminate on different racks.

Interconnections between the various ports in the LAN are typically made using "patch cables", which are usually UTP cables including four twisted pairs. Each end of a patch cable is terminated by a connector, such as an RJ-45 type connector for inserting into an RJ-45 type connector port. One end of each patch cable is connected to the port of a first cable line and the opposite end of the patch cable is connected to the port of a second cable line. By selectively connecting the a ious cable lines using the patch cables, a desired

combination of network interconnections can be achieved.

Fig. 15 shows a typical patch system organised into a server row, a cross-connect row and a network row, which include patch panels. Patch cables are used to interconnect two ports through the patch system.

In many businesses, employees of a company are assigned their own computer network access number so that the employee can interface with the company's IT infrastructure. When an employee changes office locations, it is not desirable to provide that employee with newly addressed port in the network. Rather, to preserve consistency in communications, it is preferred that the exchanges of the ports in the employee's old office be transferred to the telecommunications ports in the employee's new location. This type of move is relatively frequent. Similarly, when new employees arrive and existing employees depart, it is usually necessary for the patch cables in the network cabinet (s) to be rearranged so that each employee's exchanges can be received in the correct location.

For example, US Patent Number 5483467 describes a patching panel scanner for automatically providing an

indication of the connection pattern of the data ports within a LAN, so as to avoid the manual task of identifying and collecting cable connection information. In one embodiment, which is intended for use with shielded twisted pair cables, the scanner uses inductive couplers which are associated with the data ports. The inductive coupler is disclosed as being operative to impose a signal on the shielding of shielded network cables in order to provide an indication of the connection pattern produced by connection of the cables to a plurality of ports.

In another embodiment of US Patent Number 5483467, the scanner is coupled to each data port by "dry contact" with a dedicated conductor in a patch cable. This is difficult to implement in practice, because most network cables have to meet a particular pre-determined standard in the industry, such as the RJ-45 type standard, in which there is no free conductor which could be used for determining

interconnectivity . US Patent Number 6222908 discloses a patch cable identification and tracing syst m in which the connectors of each patch cable contain a unique identifier which can be identified by a sensor in the connector ports of a

International Patent Application Publication Number WO2005/109015, which relates to the field of cable state testing, discloses a method of determining the state of a cable comprising at least one electrical conductor and applying a generated test signal to at least one conductor of the cable by a non-electrical coupling transmitter. The reflected signal is then picked up and compared with expected state signal values for the cable, so that the state of the cable can be determined. The present inventors have found that signals coupled to a twisted pair cable by the methods described in WO2005/109015 have a tendency to leak out from the twisted pair cable, especially when other twisted pair cables are nearby.

UK patent application number GB0905361.2 (published as GB2468925), US patent application serial number 11/597575 and International patent application number PCT/GB2010/000594 , by the present inventors, and the content of which is herewith incorporated in its entirety, each describe apparatuses and methods for coupling a signal to and from a twisted pair cable by non-contact coupling with twisted pairs in the twisted pair cable, such that the signal propagates along the cable between at least two of the twisted pairs. Such signals may be used to determine interconnections, e.g. within a local area network. These patent applications generally relates to a discovery that a twisted pair cable, e.g. an unshielded twisted pair (UTP) cable, provides communication channels which are additional to the respective communication channel provided within each twisted pair in the cable. In particular, it has been found that additional communication channels exist between each combination of two twisted pairs within a twisted pair cable, due to coupling between the twisted pairs. Each combination of two twisted pairs within a twisted pair cable has been termed a "pair-to-pair" combination. Therefore, the additional communication channels may be termed "pair-to-pair" channels. Application GB0905361.2 discloses that a signal which propagates along a twisted pair cable between two of the twisted pairs can propagate reliably and over useful

Therefore the test signals can be introduced into the "pair- to-pair" channel and these the "pair-to-pair" signals can be used to monitor the operation of the network without

disrupting the normal operation of the network.

UK patent application GB1009184.1 (published as

GB2480830) , also by the present inventors, and the content of which is herewith incorporated in its entirety, discloses signal processing apparatuses and methods for use with a plurality of cable lines, e.g. cable lines including one or more twisted pair cables. In particular, GB1009184.1 relates to apparatuses and methods for analysing one or more

characteristics of a test signal coupled out from one of a plurality of cable lines. GB1009184.1 patent application presents apparatuses and methods for analysing a

characteristic of a test signal, e.g. a "pair-to-pair" signal, coupled out by a coupling unit, to determine whether that test signal has propagated directly to the coupling unit via a single cable line or has propagated indirectly to the coupling unit via crosstalk between different cable lines.

The present invention has been devised in light of the above considerations.

In general, the present invention relates to developments concerning an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the apparatus having:

a plurality of transmitter coupling nnitg,- each

transmitter coupling unit being configured to couple to a respective cable line in a network comprising a plurality of cable lines and to couple a test signal into the respective cable line; and

a plurality of receiver coupling units, each receiver coupling unit being configured to couple to a respective cable line in the network and, if a test signal is present in the respective cable line, to couple the test signal out from the respective cable line;

wherein the apparatus includes an interconnection identification means configured to identify interconnections between the transmitter coupling units and the receiver coupling units by cable lines in the network and/or a state determining means configured to determine the physical state of cable lines in the network using the transmitter coupling units and the receiver coupling units.

As described below in further detail, such an apparatus may use non-contact coupling units as disclosed in UK patent application GB0905361.2 and/or a signal processing unit as disclosed in UK patent application GB1009184.1, a copy of which is annexed hereto. The apparatus may operate in parallel with the network. The following disclosure relates to, amongst other things, an example of the hardware functionality required to realise such an apparatus; an installation sequence for the apparatus such that the apparatus can be easily fitted onto the network; and the functionality

underpinning the apparatus, which may be implemented in software .

For the avoidance of any doubt, if the apparatus is for both identifying interconnections in a network comprising a plurality of cable lines and for determining the physical state of cable lines in the network, the interconnection identification means may use the same hardware as the state determining means .

In a first aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines, the apparatus having:

a plurality of transmitter coupling units, each

transmitter coupling unit being configured to couple to a respective cable line in a network comprising a plurality of cable lines and to couple a test signal into the respective cable line;

a plurality of receiver coupling units, each receiver coupling unit being configured to couple to a respective cable line in the network and, if a test signal is present in the respective cable line, to couple the test signal out from the respective cable line; and

an interconnection identification means configured to identify interconnections between the transmitter coupling units and the receiver coupling units by cable lines in the network;

wherein the interconnection identification means is configured to, if any one of the transmitter coupling units is coupled to the same cable line as a selected one of the receiver coupling units, identify the interconnection between the transmitter coupling unit and the selected receiver coupling unit by:

(i) selecting a subset of the transmitter coupling units;

(ii) conveying, at least once, the same test signal to each of the transmitter coupling units in the selected subset at substantially the same time so that, for each of the transmitter coupling units in the selected subset that is coupled to a respective cable line, the transmitter coupling unit couples the test signal into the respective cable line;

(iii) determining whether the selected subset of

transmitter coupling units includes a transmitter coupling unit that is coupled to the same cable line as the selected receiver coupling unit based on whether the selected receiver unit couples out, from the cable line to which it is coupled, a test signal which has propagated directly to the receiver coupling unit from one of the transmitter coupling units in the selected subset; and

(iv) selecting a new subset of the transmitter coupling units based on the determination in step (iii) , and performing steps (ii) and (iii) for the newly selected transmitter coupling units; and

(v) if necessary, repeating step (iv) until the

interconnection between the transmitter coupling unit and the selected receiver coupling unit is identified.

Identifying an interconnection in this way has been found to be much more efficient in quickly identifying an

interconnection between transmitter and receiver coupling units than other methodologies, e.g. in which a test signal is coupled to the transmitter coupling units one at a time.

In this context, a signal which has propagated directly from one coupling unit to another is a signal which propagates along a cable line to which both coupling units are coupled, i.e. in contrast to a signal which propagates indirectly from one coupling unit to another e.g. via one or more coupling paths between different cable lines to which the coupling units are respectively coupled.

For the avoidance of doubt, the same test signal may be conveyed to each of the transmitter coupling units in a selected subset at substantially the same time in many different ways, e.g. by generating a test signal in a single signal generating unit and splitting the test signal so it can be conveyed to more than one transmitter coupling unit e.g. using one or more splitter unit as described below, and/or by generating the same test signal independently using a

plurality of signal generating units so that the same test signal can be conveyed to more than one transmitter coupling unit e.g. using one or more splitter unit as described below. Preferably, the interconnection identification means is also configured to identify the absence of an interconnection between the selected receiver coupling unit and any of the transmitter coupling units. Thus, the interconnection

identification means may be configured to identify either an interconnection between one of the transmitter coupling units and the selected receiver coupling unit or the absence of such an interconnection, depending on which of these conditions is true .

Accordingly, the interconnection identification means may be configured to identify either an interconnection between one of the transmitter coupling units and the selected receiver coupling unit or the absence of such an

interconnection by:

(i) selecting a subset of the transmitter coupling units;

(iii) determining whether the selected subset of

(v) if necessary, repeating step (iv) until an

interconnection between one of the transmitter coupling units and the selected receiver coupling unit or the absence of such an interconnection is identified.

The selecting of a new subset of the transmitter coupling unit in step (iv) based on the determination in step (iii) may be made according to a large number of possible search algorithms .

For example, the interconnection identification means may be further configured so that, if it is determined in step (iii) that the selected subset of transmitter coupling units includes a transmitter coupling unit that is coupled to the same cable line as the selected receiver coupling unit, then step (iv) includes:

(a) disregarding any transmitter coupling units that are not selected for the selecting of any new subsets of the transmitter coupling units; and

(b) selecting a subset of the previously selected transmitter coupling units as the new subset of the

transmitter coupling units.

Preferably, step (b) includes selecting a subset which contains half or approximately/substantially half of the previously selected transmitter coupling units as the new subset of the transmitter coupling units. This has been found to be found a particularly efficient way to identify an interconnection, and may form part of a binary tree search algorithm, e.g. as described below.

Preferably, the interconnection identification means is further configured so that, if it is determined in step (iii) that the selected subset of transmitter coupling units does not include a transmitter coupling unit that is coupled to the same cable line as the selected receiver coupling unit, then step (iv) includes: (a) disregarding any transmitter coupling units that are selected for the selecting of any new subsets of the

transmitter coupling units; and

(b) selecting all or a subset of the not selected and not disregarded transmitter coupling units as the new subset of the transmitter coupling units.

Preferably, step (b) includes selecting a subset which contains half or approximately/substantially half of the not selected and not (previously) disregarded transmitter coupling units. This has been found to be found a particularly

efficient way to identify an interconnection, and may form part of a binary tree search algorithm, e.g. as described belo .

The selecting of a new subset of the transmitter coupling unit in step (iv) based on the determination in step (iii) may be made according to a binary tree search algorithm. The binary tree search algorithm may involve, for example, initially selecting a subset preferably containing half or approximately/substantially half of the selected transmitter coupling units in step (i) . If, in step (iii) it is determined that the selected subset does not include a transmitter coupling unit that is coupled to the same cable line as the selected receiver unit, then a subset containing the remaining transmitter units is selected as a new subset in step (iv) . If, it is then determined that this subsequently selected subset does not include a transmitter coupling unit, then the absence of an interconnection between the selected receiver coupling unit and any of the transmitter coupling units can be identified. However, if it determined for either selected subset that the selected subset includes a transmitter coupling unit that is coupled to the same cable line as the selected receiver unit, then a subset preferably containing half or approximately/substantially half of the previously selected transmitter coupling units is then selected as a new subset. This can be repeated until the interconnection between B2012/000324 one of the transmitter coupling units and the selected

receiver coupling unit is identified.

In some embodiments, the determination in step (iii) of whether the selected receiver unit couples out, from the cable line to which it is coupled, a test signal which has

propagated directly to the receiver coupling unit from one of the transmitter coupling units in the selected subset, may be a trivial task if there is little or no crosstalk between cable lines in the network.

However, the presence of crosstalk between cable lines in the network may make it more difficult to determine whether the selected receiver unit couples out, from the cable line to which it is coupled, a test signal which has propagated

directly to the receiver coupling unit from one of the

transmitter coupling units in the selected subset. Crosstalk has been found to create particular difficulties for

determining whether a signal which has propagated between at least two conductors in a cable, e.g. a signal which has

propagated between two twisted pairs in a cable, has

propagated directly to the receiver coupling unit from one of the transmitter coupling units in the selected subset or has propagated indirectly, e.g. via one or more coupling paths between different cable lines. However, such difficulties can be overcome using the techniques described in UK patent

application number 1009184.1, a copy of which is annexed

hereto. In particular, this UK patent application describes how to determine whether a signal which has propagated between at least two conductors in a cable line has propagated

directly from a transmitter ("first") coupling unit to a

receiver ("second") coupling unit, by analysing one or more characteristics of the signal coupled out from a cable line by the receiver coupling unit.

Accordingly, the interconnection identification means may include a signal processing unit configured to, if any of the 0324 receiver coupling units couples out a test signal, analyse one or more characteristics of the test signal to determine, based on the one or more analysed characteristics, whether the test signal has propagated directly to the receiver coupling unit from one of the transmitter coupling units. The signal

processing unit may be configured to analyse one or more

characteristics of the test signal to determine, based on the one or more analysed characteristics, which of the following conditions is true: (i) the test signal is a direct signal which has propagated directly from a transmitter coupling unit to the receiver coupling unit via a single cable line to which the first and second coupling unit are coupled; (ii) the test signal is a crosstalk signal that has propagated indirectly from a transmitter coupling unit to the receiver coupling unit via one or more coupling paths between different cable lines to which the transmitter and receiver coupling units are

respectively coupled.

Thus, in step (iii) , the signal processing unit may be used to determine whether the selected receiver unit couples out, from the cable line to which it is coupled, a test signal which has propagated directly to the receiver coupling unit from one of the transmitter coupling units in the selected subset. The signal processing unit may be form part of a

signal analysing unit included in the interconnection

identification means.

The interconnection identification means may be

configured so that step (ii) includes conveying, more than once, the same test signal to each of the transmitter coupling units in the selected subset at substantially the same time.

Conveying the same test signal to each of the transmitter coupling units in the selected subset twice or more than twice may be useful, for example, in embodiments in which each

transmitter coupling unit includes two pairs of electrodes for coupling a voltage signal into a respective cable line by non- contact coupling with twisted pairs in the cable line so that the voltage signal propagates between two or more of the twisted pairs. Having two separate pairs of electrodes for coupling a voltage signal into a twisted pair cable was disclosed, for example, in UK patent application number

GB0905361.2, US patent application serial number 11/597575 and International patent application number PCT/GB2010 /000594 , and it is useful to avoid the problem of one of the pairs of electrodes in a transmitter coupling unit being in a "null" location such that the signal it couples into a twisted pair cable is not received by a receiver coupling unit.

Accordingly, step (ii) may in some embodiments include conveying the same signal to a first pair of electrodes in each of the transmitter coupling units in the selected subset at a substantially the same first time and then, subsequently, conveying the same signal to a second pair of electrodes in each of the transmitter coupling units in the selected subset at a substantially the same second time.

The apparatus may additionally be for determining the physical state of cable lines in the network and may therefore include a state determining means configured to determine the physical state of cable lines in the network using the transmitter coupling units and the receiver coupling units as described above.

The first aspect of the invention may provide a method including method steps corresponding to the use of an above described apparatus.

The interconnection identification means may include: at least one signal generating unit configured to generate the test signal; and

conveying means configured to convey the test signal generated by the at least one signal generating unit to the plurality of transmitter coupling units. The conveying means may include at least one splitter unit configured to receive the test signal via a single input signal path from the signal generating unit and to output the test signal via a plurality of output signal paths. Thus, the splitter unit provides a simple means to allow the conveyance of the same test signal to a plurality of the transmitter coupling units at the same time.

Each output signal path of the at least one splitter unit may include a respective switch operable to control whether a test signal is outputted via the output signal path and/or a balun. The switches may provide a convenient means for conveying the test signal only to a subset of the transmitter coupling units. Each switch (in the at least one splitter unit) may be a switchable amplifier. This helps to reduce the creation of reflections in the output signal path.

The conveying means may include at least one further splitter unit configured to receive the test signal via a single input signal path from the output signal path of a splitter unit and to output the test signal via a plurality of output signal paths (e.g. directly to electrodes of a

transmitter coupling unit) . Splitting an already split test signal in this way provides a simple means to allow the conveyance of the same test signal to a plurality of the transmitter coupling units at the same time.

Each output signal path of the at least one further splitter unit may include a respective switch operable to control whether a test signal is outputted via the output signal path and/or a balun. The switches may provide a convenient means for conveying the test signal only to a subset of the transmitter coupling units. To reduce cost, each switch (in the at least one further splitter unit) may be an analogue switch, preferably an analogue switch having a high "off" isolation. Reducing reflections in the at least one further splitter unit may not be as important as reducing reflections in the at least one splitter unit.

One or more (preferably all) of the splitter units and/or further splitter units may include a test signal detector for detecting a test signal from the at least one signal

generating unit. The or each test signal detector may be a radio frequency detector. The or each radio frequency detector may comprise an arrangement including a diode, a resistor and a capacitor.

The interconnection identification means may be

configured to identify interconnections between the signal generating unit, the splitter units and/or the further splitter units by generating test signals using the signal generating unit and detecting the test signals using one or more of the test signal detectors.

The conveying means may include switching means operable to control which of the plurality of transmitter coupling units receives the test signal from the signal generating unit. The switching means may therefore include: a respective switch located in each output signal path of at least one splitter unit; and/or a respective switch located in each output signal path of at least one further splitter units, as described above.

The interconnection identification means may include: a signal analysing unit for analysing a test signal coupled out from a cable line by one of the plurality of receiver coupling units; and

conveying means configured to convey a test signal coupled out from a cable line by one of the plurality of receiver coupling units to the signal analysing unit.

The conveying means may include switching means operable to couple any one of the plurality of receiver coupling units to the signal analysing unit via a signal path which is common to all receiver coupling units.

The switching means may include a respective switch located between each receiver coupling unit and the common signal path.

In a second aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the

apparatus having:

a plurality of transmitter coupling units, each

wherein the apparatus includes an interconnection identification means configured to identify interconnections between the transmitter coupling units and the receiver coupling units by cable lines in the network and/or a state determining means configured to determine the physical state of cable lines in the network using the transmitter coupling units and the receiver coupling units;

wherein the interconnection identification means and/or state determining means includes:

at least one signal generating unit configured to generate the test signal; and

conveying means configured to convey the test signal generated by the at least one signal generating unit to the plurality of transmitter coupling units; wherein the conveying means includes at least one splitter unit configured to receive the test signal via a single input signal path from the .signal generating unit and to output the test signal via a plurality of output signal paths .

The apparatus may have any feature described in

connection with the first aspect of the invention, e.g. at least one further splitter unit, e.g. switching means. Thus, the second aspect of the invention may provide an apparatus including such features, but without necessarily including an interconnection identification means as set out in the first aspect of the invention.

In a third aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the apparatus having: a plurality of transmitter coupling units, each

wherein the interconnection identification means and/or state determining means includes: at least one signal generating unit configured to generate the test signal; and

conveying means configured to convey the test signal generated by the at least one signal generating unit to the plurality of transmitter coupling units;

wherein the conveying means includes:

at least one splitter unit configured to receive the test signal via a single input signal path from the signal

generating unit and to output the test signal via a plurality of output signal paths;

optionally, at least one further splitter unit configured to receive the test signal via a single input signal path from the output signal path of a splitter unit and to output the test signal via a plurality of output signal paths;

wherein one or more (preferably all) of the splitter units and/or further splitter units includes a test signal detector for detecting a test signal from the at least one signal generating unit.

The apparatus may have any feature described in

connection with the first aspect of the invention, e.g. the interconnection identification means and/or state determining means may be configured to identify interconnections between the signal generating unit, the splitter units and/or the further splitter units by generating test signals using the signal generating unit and detecting the test signals using one or more of the test signal detectors. Thus, the third aspect of the invention may provide an apparatus including such features, but without necessarily including an

interconnection identification means as set out in the first aspect of the invention.

In a fourth aspect, the invention may provide, an

apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the

apparatus having: a plurality of transmitter coupling units, each

a signal analysing unit for analysing a test signal coupled out from a cable line by one of the plurality of receiver coupling units; and

conveying means configured to convey a test signal coupled out from a cable line by one of the plurality of receiver coupling units to the signal analysing unit;

wherein the conveying means includes switching means operable to couple any one of the plurality of receiver coupling units to the signal analysing unit via a signal path which is common to all receiver coupling units.

The apparatus may have any feature described in

connection with the first aspect of the invention, e.g. the switching means may include a respective switch located between each receiver coupling unit and the common signal path. Thus, the fourth aspect of the invention may provide an apparatus including such features, but without necessarily including an interconnection identification means as set out in the first aspect of the invention.

In a fifth aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the apparatus having: a plurality of transmitter coupling units, each

at least one signal generating unit configured to generate the test signal; and

a wander lead for coupling, via an additional transmitter coupling unit, the test signal generated by the at least one signal generating unit into any one of the cable lines in a network comprising a plurality of cable lines.

The wander lead may include or be coupled to the

additional transmitter coupling unit. In a sixth aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for d t-ermining the physical state of cable lines in the network, the apparatus having: a plurality of transmitter coupling units, each

wherein the interconnection identification means and/or state determining means includes at least one signal

generating and/or analysing unit configured to generate the test signal and/or analyse a test signal coupled out by one of the plurality of receiver coupling units;

wherein the at least one signal generating and/or analysing unit includes a synch block which allows the signal generating and/or analysing unit to be synchronised with other signal generating and/or analysing units.

Synchronising the signal generating and/or analysing unit is useful, for example, in using multiple signal generating units to generate the same test signal at substantially the same time, e.g. as may be useful in connection with the first aspect of the invention. In a seventh aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the

apparatus having:

a plurality of transmitter coupling units, each

wherein the interconnection identification means and/or state determining means includes at least one cable including a plurality of twisted pairs, wherein the interconnection identification means is configured such that:

a first twisted pair in the at least one cable carries a test signal generated by a signal generating unit; and/or

a second twisted pair in the cable carries a first communications signal for providing information from one component in the interconnection identification means and/or state determining means to another component in the

interconnection identification means and/or state determining means; and/or

a third twisted pair in the cable carries a second communications signal for providing information from one component in the interconnection identification means and/or state determining means to another component in the

interconnection identification means and/or state determining means,- wherein the second communications signal propagates in a direction opposite to that of the first communications signal; and/or

a fourth twisted pair in the cable carriers power for powering one or more components of the interconnection identification means.

The interconnection identification means and/or state determining means may include a signal generating unit configured to generate the test signal.

The communication signal (s) may be transmitted, for example, according to the RS485 standard. The components between which communication signals may be transmitted may include, for example, a signal generating and/or analysing unit configured to generate the test signal and/or analyse a test signal coupled out by one of the plurality of receiver coupling units; a splitter unit; and/or a further splitter unit .

In an eighth aspect, the invention may provide an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, the

apparatus having:

a plurality of transmitter coupling units, each

a plurality of receiver coupling units, each receiver coupling unit being configured to couple to a respective cable line in the network and, if a test signal is present in the respective cable line, to couple the test signal out from the respective cable line; wherein the apparatus includes an interconnection identification means configured to identify interconnections between the transmitter coupling units and the receiver coupling units by cable lines in the network and/or a state determining means configured to determine the physical state of cable lines in the network using the transmitter coupling units and the receiver coupling units;

wherein the interconnection identification means and/or state determining means is configured to perform an

installation sequence in which each transmitter coupling unit and each receiver coupling unit is associated with a

respective port in the network.

The interconnection identification means may further be configured to record in a database the association of each transmitter coupling unit and each receiver coupling unit with a respective port in the network.

The installation sequence may, comprise, for example:

(i) supplying prompts to a user;

(ii) manual inputting of data by the user in response to the prompts.

In an ninth aspect, the invention may provide a coupling unit for coupling a voltage signal to and/or

from a cable including a plurality of twisted pairs, the coupling unit having:

a first electrode and a second electrode arranged to produce an electric field therebetween to couple a voltage signal to the cable by non-contact coupling with the twisted pairs so that the voltage signal propagates along the cable between at least two of the twisted pairs and/or arranged to receive a voltage signal which has propagated along the cable between at least two of the twisted pairs by non-contact coupling with at least two of the twisted pairs between which the voltage signal has propagated; wherein the first and/or second electrodes of the coupling unit are located (preferably printed) on a flexible

The flexible circuit board provides a convenient means of providing electrodes which can easily be pressed against the sleeve of a twisted pair cable.

The first and second electrodes may be located

(preferably printed) on one side of the flexible circuit board. A ground plane may be located (preferably printed) on an opposite side of the flexible circuit board to the first and second electrodes. This arrangement helps provide

shielding for the first and second electrodes.

The flexible circuit board may have a comb (e.g. ctenoid) shape, with a plurality of projections forming the comb shape. The first and second electrodes of the coupling unit are preferably located (preferably at a distal end) on a

projection of the comb shape.

The coupling unit may have a third electrode and a second electrode arranged to produce an electric field therebetween to couple a voltage signal to the cable by non-contact coupling with the twisted pairs so that the voltage signal propagates along the cable between at least two of the twisted pairs and/or arranged to receive a voltage signal which has propagated along the cable between at least two of the twisted pairs by non-contact coupling with at least two of the twisted pairs between which the voltage signal has propagated. In this case, the third and fourth electrodes may be located on a projection of the comb shape that is different to that on which the first and second electrodes of the coupling unit are mounted .

The pairs of electrodes from other coupling units may also be located on other projections of the comb shape. The coupling unit may include a clip made of

resilient/elastic material (e.g. plastic), the clip being configured to press the first and second electrodes (and optionally the third and fourth electrodes) of the coupling unit against the sleeve of a twisted pair cable.

The flexible circuit board may include conductive pads for connecting the first and second electrodes (and optionally the third and fourth electrodes) to corresponding pads on an external circuit board.

The flexible circuit board may be configured to be connected to the external circuit board by clamping the conductive pads of the flexible circuit board against the corresponding pads of the external circuit board.

The coupling unit may be for use with any apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network, e.g. as described herein.

Any interconnection identification means and/or state determining means described herein may include at least one signal generating unit configured to generate the test signal and/or at least one signal analysing unit configured to analyse a test signal coupled out by one of the plurality of receiver coupling units. A signal generating unit and an analysing unit may be provided by a single unit, which unit may be referred to e.g. as a "scanner".

In any apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network described herein, each transmitter coupling unit may be configured to couple a test signal into a respective cable line in the network such that the test signal propagates along the respective cable line between at least two conductors in the respective cable line. The at least two conductors in the respective cable line may be twisted pairs in the cable line. Thus, each transmitter coupling unit may be configured to couple a test signal into a respective cable line in the network such that the test signal propagates along the respective cable line between at least two twisted pairs in the respective cable line.

Equally, in any apparatus for identifying

interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network described herein, each receiver coupling unit may be configured to couple a test signal out from a

respective cable line in the network after it has propagated between at least two conductors in the respective cable line. The at least two conductors in the respective cable line may be twisted pairs in the cable line. Thus, each receiver coupling unit may be configured to couple a test signal out from a respective cable line in the network after it has propagated between at least two twisted pairs in the

respective cable line.

In any apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network described herein, each transmitter coupling unit may be configured to couple a test signal into a respective cable line in the network by non-contact coupling with conductors in the respective cable line. Equally, each receiver coupling unit may be configured to couple a test signal out from a respective cable line in the network by non-contact coupling with the conductors in the respective cable line. In this context, non-contact coupling refers to coupling that does not involve direct electrical (i.e. ohmic) contact with the conductors of the cable line. Coupling units capable of coupling a test signal into (or out from) a twisted pair cable line so that the signal propagate? (or sf sr the signal has propagated) between at least two twisted pairs in the twisted pair cable line by non- contact coupling are disclosed, for example, in UK patent application number GB0905361.2, US patent application serial number 11/597575 and International patent application number PCT/GB2010/000594 , and also in UK patent application number GB1009184.1, a copy of which is annexed hereto.

Accordingly, in any apparatus for identifying

interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network described herein, each transmitter coupling unit may include any one or more of the following features: first and second electrodes arranged to produce an electric field therebetween to couple a voltage signal (which may, for example, be a test signal generated by a signal generating unit) into a twisted pair cable by non-contact coupling with twisted pairs in the twisted pair cable so that the voltage signal propagates along the twisted pair cable between at least two of the twisted pairs; electrical isolation means (e.g. a balun) arranged to electrically isolate the electrodes from the signal generating unit; shielding for shielding the electrodes from an external electromagnetic field; means for converting (e.g. a choke) a single-ended voltage signal from a signal generating unit into a differential voltage signal to be coupled to the electrodes; and a housing which may be arranged to be clipped onto a twisted pair cable.

Likewise, in any apparatus for identifying

interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network described herein, the or each receiver coupling unit may include any one or more of the following features: first and second electrodes arranged to couple a voltage signal (which may, for example, be a test signal that was coupled into one of the plurality of cable lines by a

transmitter coupling unit) out from a twisted pair cable by non-contact coupling with at least two of the twisted pairs in the twisted pair cable between which the voltage signal has propagated; electrical isolation means (e.g. a balun) arranged to electrically isolate the electrodes from the signal processing unit; shielding for shielding the electrodes from an external electromagnetic field; means for converting (e.g. a choke) a differential voltage signal from the electrodes into a single-ended voltage signal to be coupled to a signal processing unit; a housing which may be arranged to be clipped onto a twisted pair cable.

Any test signal described herein may be a signal having characteristics such that, when it is coupled out from a cable line by a receiver coupling unit, the characteristics of the test signal can be analysed to determine whether the resulting second test signal has propagated directly to the receiver coupling unit from a transmitter coupling units. The present inventors have found that signals suitable for performing time domain reflectometry or frequency domain reflectometry are suitable for such purposes. Accordingly, a test signal described herein may be a test signal suitable for performing time domain reflectometry and/or a first test signal suitable for performing frequency domain reflectometry, which may be a voltage signal.

In time domain reflectometry, a system response is measured as a function of time. A test signal suitable for time domain reflectometry might be, for example, an impulse or narrow transient test signal, e.g. having a duration of less than 10 ns (which corresponds to an electrical length of 2 metres) .

In frequency domain reflectometry , a system response is measured as a function of frequency. A test signal suitable for frequency domain reflectometry might be, for example, a frequency swept sine wave or pseudo random noise. Frequency domain information can be converted into a corresponding time domain response via an inverse Fourier transform, as would be known to those skilled in the art.

In any apparatus for determining the physical state of cable lines in a network described herein, a state determining means may be configured to determine the physical state of a cable line in the network e.g. by coupling a test signal into a selected cable line using one of the transmitter coupling units, coupling a test signal out of the selected cable line using one of the receiver coupling units and analysing, e.g. in a signal analysing unit, the test signal coupled out of the selected cable line by the receiver coupling unit so as to determine a physical state of the cable. For example, the physical state of the cable line may be determined by

comparing a received test signal with a reference test signal, as is known in the art of reflectometry . An apparatus for determining the physical state of cable lines in a network is shown, for example, in Fig. 17.

Herein, the term "cable" preferably refers to any cable capable of carrying a signal, e.g. a voltage signal or an optical signal. The term "cable line" preferably refers to either a cable or a plurality of cables connected together so as to be capable of carrying a signal. In some embodiments, the term "cable" may refer to a cable including at least two conductors. In some embodiments, the term "cable line" may refer to either one such cable or to a plurality of such cables whose conductors have been directly, i.e. by direct electrical ("ohmic") contact, coupled together.

Herein, when it is described herein that a signal propagates "between" at least two conductors in a cable line, it is meant that the signal propagates along the cable line due to a coupling between the conductors, the signal being difference in state between the conductors. Such a signal is commonly referred to as "differential" signal. A differential signal is therefore distinguished from a so-called "common mode" signal, where all the conductors have substantially the same state and the signal is a difference in state between all the conductors and an external reference (e.g. ground) .

For example, a signal that propagates between at least two conductors in a cable line may be a voltage signal, i.e. a difference in voltage between at least two conductors in the cable line, which propagates along the cable line due to inductive and capacitive coupling between at least two conductors. Here, the capacitance per metre and inductance per metre will generally determine e.g. the speed of propagation of such a voltage signal.

For the avoidance of doubt, when a signal is described herein as propagating along a cable line, the signal does not have to propagate along the entire length of the cable line. Likewise, when a signal is described herein as having

propagated along a cable line, the signal does not have to have propagated along the entire length of the cable line.

In another aspect of the invention, there may be provided a kit of parts for forming an apparatus as set out in any above aspect, e.g. an apparatus for identifying

interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network. The kit of parts may include, for example, a plurality of transmitter coupling units, and/or a plurality of receiver coupling units, and/or an interconnection

identification means, and/or a state determining means as set out above and/or subcomponents thereof.

In another aspect of the invention, there may be provided any component of an apparatus as set out in any above aspect, e.g. an apparatus for identifying interconnections in a network comprising a plurality of cable lines and/or for determining the physical state of cable lines in the network. The component may be, for example, a transmitter coupling unit, a receiver coupling unit, an interconnection

identification means or a state determining means as set out above, or a subcomponent thereof.

In another aspect of the invention, there may be provided a method which may include any method step corresponding to the use of any apparatus or apparatus feature described in connection with any above aspect of the invention.

The invention also includes any combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Fig. 15 shows a typical patch system organised into a server row, a cross-connect row and a network row.

Fig. 16 is a block diagram of a system configured to determine interconnection status such as a map of the patch leads with a local area network.

Fig. 17 is a block diagram of a system configured to monitoring the physical status of the channels within the network. It will be apparent to one skilled in the art that an apparatus could be configured to have the functionality of the systems shown in both Fig 16 and Fig 17. The two functions have been illustrated in separate drawings in this application for clarity.

Fig. 18 is a representation illustrating the main component blocks contained with the "Scanners" shown in Figs. 16 and 17.

Fig. 19 is a representation of the main circuit blocks contained in the "24 way splitter" shown in Figs. 16 and 17.

Fig. 20 is a representation the interconnection details between the "24 way splitter" and the "Tx front end units". Fig. 21 is a representation of the main circuit blocks contained in the "Tx Front End units" shown in Figs. 16 and 17.

Fig. 22 is a representation of the main circuit blocks contained in the "Rx Front End units" shown in Figs. 16 and 17.

Figs. 23 (a) -(d) are representations showing the use of flexible printed circuit for implementing the transmitter and/or receiver plates.

Fig. 24 is a representation showing how the transmitter and/or receiver plates can be clipped around the cable in a format that can be easily deployed in the field.

Figs. 16 and 17 show block diagrams for the system hardware. The system preferably has two main modes of operation in which Fig. 16 shows the system operating in a "patching" mode, whereby the system determines a connectivity map of the patch cable, which the user has inserted in between the patch panels to configure the local area network. Fig. 17 shows the system operating in a "monitoring" mode whereby the system inspects each channel on the network e.g. by performing reflectometry to look for impedance changes in each channel. Any impedance changes may indicate a change in status of the channel such as a fault in the cable or a unit being unplugged at the end of the channel. The system is preferably

controlled by a host PC, which is connected to one or more scanner units. In this example, Ethernet, which is labelled IP, is used to provide communications between each scanner unit and the host PC. The host PC preferably reports

information about the network and receives instructions over the Internet, labelled as the Cloud. The system may be controlled by programmes which are either local on the host PC or hosted on external resources in the Cloud via external service providers.

Referring to Fig 16, the system preferably determines a connectivity map by applying a test signal to one or more transmitter coupling units, which are labelled "Tx plates", and then monitors the signal from one or more receiver coupling units, labelled "Rx plates". The transmitter coupling units and the receiver coupling units may typically be placed directly behind the patch panels. An adequate number coupling units is preferably used such that a full connectivity map between all relevant ports can be determined by the system. Any test signal received by the Rx plates is preferably analysed by signal processing algorithms, such as those described in GB1009184.1, to determine if the signal has been conveyed directly between the transmitter coupling unit and the receiver coupling unit, in which case there is a patch lead present, or via an unwanted route, such as alien

crosstalk between UTP cables in the network. The system preferably implements a search algorithm to determine all the directly conveyed signal paths between every transmitter coupling unit and every receiver coupling unit. Each directly conveyed signal path is evidence of a patch lead connected between the respective ports. The search algorithm preferably ensures that all possible patch lead positions are examined in an efficient manner. One possible search algorithm is a binary tree in which half the possible interconnections from the ports with transmitter coupling units a port with a receiver coupling unit are tested first; if the result shows no direct connection then the other half of the possible interconnections are tested; if the result shows no direct connection then no patch lead is present; alternatively if a direct connection is detected on either half, then the algorithm tests one quarter of the remaining possible

interconnections; then one eight etc until the presence of a interconnection or not has been established. It should be noted that there are many variations on this theme and although a binary tree search is thought to be the most efficient, any structured and logical search may in practice be performed by the system to ensure that all possible direct connections are determined. In order to apply the test signal to one or more transmitter coupling units, the system preferably contains as series of splitters and Tx front end coupling couplings, which contain switches or switched amplifiers as appropriate to convey the test signal to one or any combination of

transmitter coupling units as required. The internal

operation of the splitter and Tx front end units are shown in Figs. 19 and 21 respectively. In addition, the scanner may provide an output for a wander lead, which might simply be a transmitter coupling unit on a free lead. The wander lead may be hand held or attached to any accessible cable in the network as required by the user to test the connectivity of a particular port or cable.

The structure of UTP is such that the individual twisted pairs are held together by a sleeve. Within the sleeve, the bundle of twisted pairs is also twisted by the manufacturers with an overall twist rate, with a value denoted here as lambda. It is highly preferable to ensure that both the transmitter coupling units and receiver coupling units are positioned next to the same corresponding pairs inside the sleeve of the UTP cable. Unfortunately, the sleeve is usually not transparent and consequently the correct position of the coupling units cannot easily be determined. To overcome this problem two transmitter coupling units are preferably deployed on each cable as shown. The two transmitter coupling units are preferably aligned in the same radial direction, but preferably spaced by lambda/4, which helps to ensure that one of the two coupling units will have good coupling to the corresponding pairs under the appropriate receiver coupling unit .

The signal received by any receiver coupling unit can be conveyed back to a scanner by a switching network contained in the Rx front end units and a radio frequency bus, such as a coaxial cable, labelled Rx coax. The internal operation of an Rx front end unit and its connection to the Rx coax is shown in Fig. 22.

The scanner units typically have the provision to service several splitter units and several Rx coax buses with multiple inputs and outputs of these types. This helps to ensure that a moderately sized network, such as one containing 500 ports can have the patch lead connectivity map determined with a single controller unit. For larger networks, multiple controller units may be needed in which case the timing of the signal capture and processing operation must be synchronised. Synchronisation can be achieved using dedicated connections between the scanner units. Typically one scanner unit will be programmed or configured to serve as the master and provide the necessary synchronisation signal to the other scanner units .

Communication between the scanner and the associated splitter and front end units is preferably achieved with a communication bus. A serial bus such as RS485 is a convenient means of implementing this communication as this can be connected in a daisy chain fashion around the respective units .

It should be noted that the architecture of Fig. 16 is preferably such that the delay that the transmitter test signal encounters from the scanner to the transmitter coupling units are approximately the same for all transmitter coupling units assuming that similar cable lengths are used for corresponding paths in the system. This helps to ensure that directly connected paths in the network are easy to identify by the signal processing algorithms later.

Fig. 17 shows the operation of the system when operating in the "monitoring" mode. Here only the relevant system block as shown. The monitoring functionality is preferably achieved using reflectometry . Reflectometry is an established technique which is well known by those skilled in the art of signal processing. Reflectometry can be implemented in a number of ways such as time domain reflectometry , frequency domain reflectometry and the like. The chosen method for this system is to perform reflectometry in the frequency domain, however other approaches are viable. Consequently, the scanner units preferably generate a test signal consisting of a wide band sweep of frequencies from 1 to 100 MHz, which typically contain 128 or 256 individual frequency values, which may be equally spaced. A similar test signal may also used for the "patching" mode described earlier.

The system preferably implements reflectometry by using a transmitter coupling unit to transmit the reflectometry signal and a receiver coupling unit to receive the reflectometry signal. The two coupling units are preferably positioned at integer multiplies of lambda/2 to ensure adequate coupling to the same twisted pairs inside the sleeve of the UTP cable in a similar manner to that described earlier for "patching" mode. The system can be economically implemented using a transmitter coupling units and receiver coupling units in combinations to connect to their respective coupling units behind each patch panel. The association of pairs of transmitter and receiver front end units may be controlled using direct RS485

communications between them.

Fig. 18 shows a block diagram of the internal components inside a scanner unit. The scanners preferably contain a processor in this case a moderately powerful microcontroller, labelled μθ, which communicates with the host PC via Ethernet and the splitter, Rx front end and Tx front end units using RS485. The microcontroller preferably contains the programmes necessary to control the units responsible for signal

generation and signal acquisition. The circuit preferably used to synchronise scanner units is also shown. The

synchronisation circuits help to ensure that the multiple scanner units can operate at the same clock frequency and that time critical signal acquisition and signal process function occur simultaneously. For example the synchronisation helps to ensure phase coherence during the capture and demodulation of the frequency sweeps. The signal processing functions such as digital demodulation is preferably performed by the field programmable gate array (FPGA) . The FPGA controllers the signal generator, which is preferably a direct digital synthesiser (DDS) , and which preferably generates the

frequency sweep test signals described earlier. The DDS also preferably generates the reference frequency (f - f_IF) for the multiplier. The reference frequency is preferably offset by a fixed value to representing the intermediate frequency in the heterodyne demodulation scheme. The output from the DDS is also preferably conveyed to one or more outputs for the splitter and Tx front end units described earlier. Switchable amplifiers with enable lines (EN) are preferably used to select to activate the appropriate transmitter output on the scanner unit in order to convey the transmitter signal to the rest of the system as required. Twisted pair is preferably used as a convenient and low cost transmission medium for the transmitter signals. Baluns may also be added to help reduce the common mode signal applied the twisted pairs, which helps to minimise crosstalk in the system.

The signal capture scheme may consist of a relatively standard heterodyne demodulation method. The signal input is preferably conveyed to an analogue demodulator which contains a multiplier and a low pass filter as is common practice for such demodulators. The offset in frequency between the input signal and reference preferably results in a signal at the input to the analogue to digital converter (ADC) with a frequency of f_IF. The ADC signal preferably digitises this signal and the FPGA preferably implements a digital

demodulation algorithm to determine the in-phase and

quadrature values of the signal at each value of frequency contained in the frequency sweep. The scanner preferably uses a multiplier arrangement to select one of several possible receiver signals. The receiver signals are preferably relatively small and preferably require amplification and should be conveyed to the scanner using a good quality transmission medium such as coaxial cable.

Fig. 19 shows the internal circuitry of the splitter unit, which may contain 24 outputs. All signal lines are preferably differential. The input signal, RF In is

preferably passed first passed through a balun to reject common mode signal components and then a buffer preferably helps to ensure that the input signal line is correctly matched to the input impedance of the splitter unit.

Similarly output baluns and buffers amplifiers are preferably used to help minimise common mode interference in the system and match to the output lines, RF Out 1, RF Out 2, RF Out 3, etc. respectively. The output buffers are preferably of a switchable type such that their outputs can be switched on or off by the corresponding enable line, EN1, EN2, EN3 etc. A low power microcontroller such as a PIC type with an RS485 interface can be used to activate the appropriated RF Out lines as required by commands send along the RS485 bus. The splitter preferably also contains components for DC power management and LEDs for indication of functionality to the user, but these miscellaneous and ancillary components are not shown, which is the case for the main sub-units described in this document.

Fig. 20 contains an illustration of the routing of the lines for the RF transmitter signals, the RS485 communications serial communications bus, and the two DC power levels between the splitter unit and the Tx front end units. In this particular system, UTP and RJ45 connectors have been used as a convenient and economical means of conveying these lines. As shown, one UTP cable containing 4 twisted pairs can convey the RS485, signal and power lines, with the RS485 connected following a daisy chain path out and back between the splitter unit and the Tx front end units. This connection scheme preferably requires that the RJ45 connectors (Tx FE1, Tx FE2, etc in Fig. 16) are populated in a strict sequence to ensure continuity of the RS485 line through all the transmitter front end units. In addition a 100 ohm termination is preferably be inserted in the first free Tx FE socket to help ensure that the RS485 bus is correctly terminated, thereby avoiding unwanted reflections and corrupted data.

Fig. 21 depicts the operation of a transmitter front end unit. This is similar in nature to the splitter unit shown in Fig. 19 and previously described earlier. For the purposes of brevity only the essential differences will be described.

First analogue switches are preferably used at the output as a lower cost and lower power alternative to switchable

amplifiers. The outputs of the transmitter front end unit are preferably fed directly via short leads, typically 10 cm to the plates in the transmitter coupling units. Consequently such short leads do not need driving with buffer amplifiers. Second, the transmitter front end unit is preferably made in section of 12 channels for convenience as many patch panels are 24 ports wide. The multiple of 12 allows the signal to be fed into the middle of the Tx FE signal to feed into a connector positioned in the middle of the unit. Third the transmitter front end unit preferably contains 48 output channels this is to accommodate to coupling units per cable on a 24 port patch panel. Four, a simple RF detect signal, typically consisting of a diode, resistor and capacitor is preferably used to detect when a transmitter signal has been applied to the RF In input. This is used later in the installation sequence to detect which transmitter front end units are connected to which outputs on the splitter and determine coincidence between their corresponding individual addresses stored on the programmes on each of the PIC

microcontrollers .

Fig. 22 shows the architecture of a receiver front end unit. There are structural similarities between the converse functions on the transmitter side described for the splitter unit in Fig. 19 and the transmitter front end unit in Fig. 21. Therefore for brevity only the key functional differences will be described here. First, of course the signal flow is in the opposite direction. Baluns are an useful feature on the input to help to ensure that the common mode signal is rejected and mainly the desired component, such as the pair to pair component is conveyed to the following stages. Second, amplifiers are useful at the input to both amplify the signal and present the required input impedance to the receiver coupling unit. The amplifiers preferably have switchable outputs such that the required receiver coupling unit signal is conveyed to the output. Cleary only one or no input amplifiers are enabled at a time. At the output, the signal is preferably routed through a pair of switch switches which serve a changeover function. This is typically a good quality switch such as a screen RF reed relay to preserve the

integrity of transmission for signals on the Rx coax bus. The changeover switch preferably either connects the signal from this receiver front end unit to the Rx coax bus or passes the bus through to the next receiver front end unit in the chain.

Figs. 23 (a) -(d) shows the construction of the coupling units. In particular, Fig. 23(a) highlights the use of flexible printed board (PCB) material such as polyimide as a convenient and inexpensive means of realising the pair of plates required in either the transmitter coupling unit or the receiver coupling unit. Fig. 23(b) show the view from the plate (i.e. electrode) side and Fig. 23(c) is an illustration of the view from the ground plane side. The ground plane serves an useful electromagnetic screening role. Fig. 23(d) shows how the individual elements for each coupling unit can be combined to form limbs of a comb shape (ctenoid) structure for ease of connection to a rigid PCB. To avoid a further soldering operation the metal conducting pads on the flexible PCB can be pressed directly against corresponding aligned and positioned conducting pads on the rigid PCB containing the circuitry for the receiver front end unit.

Fig. 24 illustrates the design in schematic view of a compliant elastic clip which may be used to press the plates on the flexible PCB against the sleeve of the UTP cable. An end view of the clip is provided here with the flexible PCB and the UTP cable in the middle.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or integers.

limitation of the embodiments described herein.

Claims

CLAIMS :

1. A coupling unit for use with a twisted pair cable, the coupling unit having:

2. A coupling unit according to claim 1, wherein the coupling unit has:

at least one first electrode that is adjacent to one or more first conductive elements of the coupling unit; and

at least one second electrode that is adjacent to one or more second conductive elements of the coupling unit;

wherein the at least one first electrode and the at least one second electrode are configured to transmit a differential voltage signal to the first and second conductive elements by non-contact coupling with the first and second conductive elements and/or to receive a differential voltage signal from the first and second conductive elements by non-contact coupling with the first and second conductive elements.

3. A coupling unit according to claim 2, wherein the coupling unit includes electromagnetic shielding arranged to shield the at least one first electrode from the at least one second electrode and/or electromagnetic shielding arranged to shield the one or more first conductive elements from the one or more second conductive elements.

4. A coupling unit according to claim 2 or 3 wherein the coupling unit has :

5. A coupling unit according to any one of claims 2 to 4 wherein the coupling unit has:

6. A coupling unit according to claim 2 or 3 wherein the coupling unit has:

at least one first transceiver electrode that is adjacent to the one or more first conductive elements of the coupling unit; and at least one second transceiver electrode that is adjacent to the one or more second conductive elements of the coupling unit;

wherein the at least one first transceiver electrode and the at least one second transceiver electrode are configured to transmit a differential voltage signal to the first and second conductive elements by non-contact coupling with the first and second conductive elements and to receive a

differential voltage signal from the first and second

7. A coupling unit according to claim 1 wherein the at least one electrode adjacent to the one or more conductive elements is configured to transmit a single-ended voltage signal to the one or more conductive elements by non-contact coupling with the one or more conductive elements and/or to receive a single-ended voltage signal from the one or more conductive elements by non-contact coupling with the one or more

conductive elements.

8. A coupling unit according to claim 7 wherein the coupling unit has:

9. A coupling unit according to claim 7 or 8 wherein the coupling unit has:

10. A coupling unit according to claim 7 wherein the coupling unit has:

conductive elements and to receive a single-ended voltage signal from the one or more conductive elements by non-contact coupling with the one or more conductive elements.

11. A coupling unit according to any one of the previous claims wherein the twisted pair cable is a shielded twisted pair cable including electromagnetic shielding.

12. A coupling unit according to any one of the previous claims wherein the coupling unit includes electromagnetic shielding including any one or more of:

electromagnetic shielding arranged to shield at least one first electrode from at least one second electrode;

electromagnetic shielding arranged to shield one or more first conductive elements from one or more second conductive elements ;

electromagnetic shielding arranged to shield at least one transmitter electrode from at least one receiver electrode; and/or

electromagnetic shielding arranged to shield the

conductive elements from external electromagnetic interference for the coupling unit and/or reduce crosstalk between coupling units .

13. A coupling unit according to any one of the previous claims wherein the coupling unit includes electromagnetic shielding, and the electromagnetic shielding of the coupling unit is configured to electrically connect to the

electromagnetic shielding of a shielded twisted pair cable, if the coupling unit is physically connected to the twisted pair cable by an interface of the coupling unit.

14. A coupling unit according to any one of the previous claims wherein the coupling unit includes electromagnetic shielding, and the electromagnetic shielding of the coupling unit is configured to electrically connect to a local ground.

15. A coupling unit according to any one of the previous claims wherein the coupling unit includes:

16. A coupling unit according to any one of the previous claims wherein:

the conductive elements of the coupling unit are grouped in one or more pairs, with the or each pair of conductive elements being configured to be electrically connected to both conductors of a respective twisted pair of a twisted pair cable, if the twisted pair cable is physically connected to the coupling unit by the interface; and

the or each electrode of the coupling unit is adjacent to one or more pairs of conductive elements of the coupling unit.

17. A coupling unit according to any one of the previous claims wherein the coupling unit includes:

a plurality of pairs of conductive elements; and electromagnetic shielding arranged to shield each pair of conductive elements from the other pair(s) of conductive elements .

18. A coupling unit according to any one of the previous claims wherein the or each electrode of the coupling unit is provided in the form of a respective plate having an area of 10 mm² or larger, or 20 mm² or larger.

19. A coupling unit according to any one of the previous claims wherein one or more electrodes of the coupling unit is/are printed on one or more flexible circuit boards.

20. A coupling unit according to any one of the previous claims wherein the coupling unit has a housing that houses the or each electrode and the conductive elements.

21. A coupling unit according to claim 20, wherein the housing includes a plastic inner body surrounded by a metal shell, with the metal shell providing electromagnetic

shielding arranged to shield the conductive elements from external electromagnetic interference and/or reduce crosstalk between coupling units.

22. A coupling unit according to any one of the previous claims wherein the coupling unit includes one or more

connectors for conveying a voltage signal produced by a voltage signal producing and/or processing apparatus to at least one electrode of the coupling unit and/or for conveying a voltage signal received by at least one electrode of the coupling unit to a voltage signal producing and/or processing apparatus .

23. An apparatus having:

one or more coupling units according to any one of the previous claims; a voltage signal producing and/or processing apparatus configured :

to produce a voltage signal and to convey the voltage signal to at least one electrode of the coupling unit; and/or to process a voltage signal conveyed from at least one electrode of the coupling unit.

24. A network monitoring apparatus for monitoring a network, the network monitoring apparatus having:

one or more coupling units according to any one of claims 1 to 22, the or each coupling unit being associated or configured to be associated with a respective network port in a network; and

a voltage signal producing and/or processing apparatus, wherein the voltage signal producing and/or processing apparatus is configured to produce a voltage signal and to convey the voltage signal to at least one electrode of one or more of the coupling units and/or to process a voltage signal conveyed from at least one electrode of one or more of the coupling units.

25. A network monitoring apparatus according to claim 24, wherein the network monitoring apparatus is configured to monitor a network by identifying one or more interconnections between network ports within a network and/or by determining the physical condition or state of one or more channels within a network.

26. A network monitoring apparatus according to claim 24 or 25, wherein the or each coupling unit is installed in a patch panel of the network.

27. A network monitoring apparatus according to any one of claims 24 to 26 wherein the or each coupling unit forms an integral part of a patch panel.

Ill

28. A network monitoring apparatus according to any one of claims 24 to 26 wherein the or each coupling unit is

retrofitted to a patch panel.

29. A kit of parts for forming a network monitoring

apparatus, the kit of parts having:

one or more coupling units according to any one of claims 1 to 22, the or each coupling unit being configured to be associated with a respective network port in a network; and a voltage signal producing and/or processing apparatus, wherein the voltage signal producing and/or processing apparatus is configured to produce a voltage signal and to convey the voltage signal to at least one electrode of one or more of the coupling units and/or to process a voltage signal conveyed from at least one electrode of one or more of the coupling units.

30. A method of using a coupling unit to transmit and/or receive a voltage signal, wherein the method includes:

conductive elements.

31. A method of converting a coupling unit having:

wherein the method includes:

conductive elements.

32. Ά coupling unit or apparatus substantially as any one embodiment herein described with reference to and as shown in the accompanying drawings .

33. A method substantially as any one embodiment herein described with reference to and as shown in the accompanying drawings .