WO2001043321A2

WO2001043321A2 - Monitored switch apparatus for signal recovery in catv networks using a redundant link___________________________________________

Info

Publication number: WO2001043321A2
Application number: PCT/US2000/033096
Authority: WO
Inventors: John C. Keller; Rick Oftedahl; Sara Manderfield; Jeffrey O. Brown; Craig Carlson
Original assignee: Adc Telecommunications, Inc.
Priority date: 1999-12-13
Filing date: 2000-12-06
Publication date: 2001-06-14
Also published as: WO2001043321A3; AU1950501A

Abstract

A monitored redundant switch apparatus provides an improved isolation between selected and unselected signals while using as few detectors as possible. The switch apparatus is capable of simultaneously and continuously monitoring both selected and unselected signals. The switch apparatus can be controlled remotely. In one embodiment, the switch apparatus includes a plurality of switches switching between primary signals and backup signals, a first detector coupled to monitor a condition of the selected signals, and a second detector coupled to monitor a condition of the unselected signals.

Description

MONITORED REDUNDANT SWITCH APPARATUS AND METHOD

This application is being filed as a PCT International Patent application in the name of ADC Telecommunications, Inc., a U.S. national corporation (applicant for all countries) on 06 December 2000.

Field of the Invention

The present invention relates to transmission of broad band signals in audio, video, and data transmission systems, and more particularly, to an improved switch apparatus in audio, video, and data transmission systems.

Background of the Invention

In recent years, the cable television industry has grown tremendously, with the likelihood of continuing to grow in future years. Future growth could enable the cable television industry to provide hundreds, possibly thousands of cable television channels to consumers. As the cable television industry offers more and more channels, it has become increasingly important to maintain a higher level of signal quality and to minimize breakdowns in cable television systems in order to avoid loss of service to customers.

It is known that failures or breakdowns in the transmission of audio, video, or data signals occur due to various circumstances such as a cable line cut, optic-electric converter malfunctions, bad electrical connections, amplifier failure, and switch relay malfunctions, etc. To minimize failures or breakdowns, a redundant line of signals is often used as a backup so that if a primary line of signals fail, the redundant line of signals are ready to be used. A switch, for example, an A/B switch, is used to switch from the primary line which is usually connected to a first port, of the switch to the redundant line which is usually connected to a second port, of the switch when a failure occurs on the primary line. Accordingly, signals either from the primary line or the redundant line are sent down the transmission line from the output of the A/B switch. Once a failure on the primary line is fixed, the A/B switch switches the connection back to the primary line.

It is important that failures in transmission be detected. A detector is often used in existing A/B switches to detect a failure. More particularly, a detector has been used to monitor the line currently in use, i.e., the selected line. For example, as shown in FIG. 1, a detector 108 monitors the output 104, of an A/B switch 100. If a failure is detected at the output, indicating that there is a fault in the selected line, the input of the switch is switched to the other port. Generally, port A is coupled to primary lines 102 and port B is coupled to redundant lines 106. Thus, if a fault is detected in the primary lines, the input of the switch is switched to port B so that the redundant line is now operatively coupled to the output of the switch. Because only the selected line is monitored, switching occurs without any information concerning the usability of the redundant path, i.e., whether there is a failure in the redundant path.

Alternatively, as shown in FIG. 2, a detector 118 is operatively coupled to monitor one input of the switch, in this case the primary line 112 at port A. Again, no monitoring of the unselected or redundant path 116 takes place. Also, in existing A/B switches, the port that is coupled to the unselected signals is not terminated as shown in FIGS. 1 and 2. When port A is selected, port B is not terminated, i.e. port B is not coupled to ground. This results in unwanted reflections at port B. The same is true for port A when the signals at port B are the selected signals. Thus, it is desirable to provide termination in an A B switch for the unselected signal path. It is thus desirable to provide a system and method of monitoring both the primary and redundant channels simultaneously. It is also desirable to provide a system and method for conveying the status of both the primary and redundant channels to a remote location which can be viewed by a network administrator, for example. Also, it has been known to convey measurements made by a detector such as that shown in FIGS. 1 and 2 in a switch to a remote location, for example, a computer located at the head-end of a cable plant. While information concerning the selected line was conveyed, no information concerning the unselected line was provided. In addition, while a network administrator was able to monitor the selected line, the administrator had no way of actually controlling the operation or characteristics of the switch. For example, if a switch needed to be recalibrated or thresholds set or adjusted, a service person had to be dispatched to the physical location of the switch to perform those functions. As can be appreciated this is a time consuming and costly procedure. It is thus desirable to be able to remotely monitor and control the operation and characteristics of a switch or a network of switches.

Summary of the Invention

In accordance with the present invention, the above and other problems were solved by providing a monitored redundant switch apparatus which provides an improved isolation between selected and unselected signals while using as few detectors as possible. The switch apparatus is capable of monitoring unselected signals at a termination. The switch apparatus can be controlled remotely.

According to a first aspect of the invention, there is provided a switch that includes a first input port, a second input port, and an output port. The switch has two positions such that when the switch is in a first position, the first input port is coupled to the output port to define a selected signal path and the second input port defines an unselected signal path and when the switch is in a second position, the second input port is coupled to the output port to define a selected signal path and the first input port defines an unselected signal path. Also included is a first detector coupled to the selected signal path through which a selected signal will flow to monitor the selected signal and a second detector coupled to the unselected signal path through which an unselected signal will flow to monitor the unselected signal.

According to a second aspect of the invention there is provided, a switch apparatus that includes a first switch switching between a first position which operatively couples a first input to an output to define a selected signal path and a second position which operatively couples the first input to a termination to define an unselected signal path and a second switch switching between a first position which operatively couples a second input to the output to define a selected signal path and a second position which operatively couples the second input to the termination to provide an unselected signal path wherein when the first switch is in its first portion, the second switch is in its second position and whether the first switch is in its second position, the second switch is in its first position. Also included is a first detector for continuously monitoring the selected signal and a second detector for continuously monitoring the unselected signal. According to a third aspect of the invention, there is provided a method of providing reliable switching in a switch. The method includes the steps of (a) providing a selected signal path through the switch, (b) providing an unselected signal path through the switch and (c) simultaneously monitoring the selected signal path and the unselected signal path. According to a fourth aspect of the invention, the is provided a method of remotely controlling a switch. The method includes the steps of (a) generating a graphical user interface on a computing device located externally and remotely from a switch, (b) determining what switch is operatively coupled to the computing device, and (c) displaying status information concerning both a selected signal and an unselected signal of the switch operatively coupled to the computing device on a display.

According to a fifth aspect of the invention, there is provided a system for remotely monitoring and controlling a network of switches. The system includes a general purpose computing device operatively coupled to the network, a computer program including one or more program modules executable by the computing device. The program modules include a network topology module for generating a display at the computing device of the topology of the network, a user interface module for interpreting inputs provided by a user, a network interface module for transmitting messages to the network and receiving messages from the network.

According to a sixth aspect of the invention, there is provided a method of switching between a first line of signals coupled to a first switch and a second line of signals coupled to a second switch. The method includes the steps of connecting a third switch to the first switch such that the first line of signals are selected and sent to an output line coupled to the third switch, and the second line of signals are unselected and terminated at a termination of the second switch. It also includes monitoring a condition of the selected first line of signals and a condition of the unselected second line of signals: when the condition of the selected first line of signals reaches a predetermined condition, and the condition of the unselected second line of the signals maintains at a predetermined condition, the third switch is switched to connect to the second switch such that the second line of signals are selected and sent to the output line coupled to the third switch, and the first line of signals are unselected and terminated at a termination of the first switch.

According to a seventh aspect of the invention, there is provided a method of switching between a first line of signals coupled to a first switch and a second line of signals coupled to a second switch. The method includes the steps of connecting a third switch to the first switch such that the first line of signals are selected and sent to an output line coupled to the third switch, and the second line of signals are unselected and terminated at a termination of the second switch. It also includes the step of monitoring a condition of the selected first line of signals: when the condition of the selected first line of signals reaches a predetermined condition, the third switch is switched to connect to the second switch such that the second line of signals are selected and sent to the output line coupled to the third switch, and the first line of signals are unselected and terminated at a termination of the first switch.

These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and the associated drawings.

Brief Description of the Drawings FIGS. 1 and 2 are schematic views of redundant A/B switches according to the prior art. FIG. 3 is a schematic view of a preferred embodiment of an A/B switch according to the present invention located in a cable television environment.

FIGS. 4a and 4b are a detailed diagram of the circuitry of a switch according to a preferred embodiment of the present invention. FIG. 5 is a schematic view of a preferred embodiment of remotely controlled network environment according to the present invention.

FIG. 6 is a flow chart of the software resident on the e controller of the switch shown in FIG. 3.

FIG. 7 is a flow chart of the software resident of the controller of a split signal switch according to a preferred embodiment of the present invention.

FIG. 8 is a schematic of a redundant amplifier switch according to a preferred embodiment of the present invention.

FIG. 9 is a flow chart of the software resident on the controller of the redundant amplifier shown in FIG. 8. FIG. 10 is a flow chart of the detection software resident on the controller of a switch according to a preferred embodiment of the present invention.

FIG. 11 is a flow chart of the communication and control software between the remote controller and the network environment.

FIG. 12 is a screen shot displayed at the remote controller according to a preferred embodiment of the present invention.

FIG. 13 is an alternate preferred embodiment of an A/B switch according to the present invention.

Detailed Description of the Preferred Embodiments

The present invention provides a monitored redundant switch which has improved isolation between selected and unselected signals, is capable of monitoring unselected signals, and can be controlled remotely.

Before describing in detail a particular embodiment of a monitored redundant switch in accordance with the present invention, it should be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention, and that the present invention resides primarily in a novel structural combination of conventional signal processing and communication circuits and components and not in the particular detailed configurations thereof. Accordingly, the structure, arrangement, and control of these conventional circuits and components have been illustrated by readily understandable block diagrams which show only those specific details that are pertinent to the present invention, so as not to obscure the disclosure with structural details which will be readily apparent to those skilled in the art having the benefit of the description herein. Thus, the block diagram illustrations of the figures do not necessarily represent the electrical or mechanical structural arrangement of an exemplary system or circuitry, but are primarily intended to illustrate the major structural components of the system or circuitry in a convenient functional group, so that the present invention may be more readily understood.

FIG. 3 is a schematic view of a preferred embodiment of an A B switch 120 according to the present invention located in a cable television environment. Generally, the present invention relates to a switch 120 for use in connection with a head-end 22 of a cable television system. In this preferred embodiment the switch 120 has two input ports A and B and an output port. In a preferred embodiment, port A is operatively coupled to primary channels 126 through optical-to-electrical converter 32 and port B is operatively coupled to redundant or backup channels 138 through optical-to-electrical converter 34. Under normal operating conditions, the primaiy channels on port A are operatively coupled to the output port of the switch. If a failure is detected, the input of the switch is switched to port B so that the switch operatively couples the redundant channels present at port B to the output port of the switch as will be described in detail hereafter. Once the fault is cleared on the primary channels, the input of the switch is switched back to port A. In another embodiment, the switch can be adapted for multiple split signal primary channels.

In FIG. 3, there is generally illustrated the switch 120 for use with a head-end 22, such as a receiver with modulators, and a cable plant 24. such as a set of distributor coaxial cables, in a cable television system. The received electrical signals are transmitted on both primary channels 126 and backup channels 138. As previously described, the backup channels 138 provide a backup for the primary channels in case there is a failure in the primary channels. The primary channels may be split into two or more parts as is well known, whereas the backup channels are preferably not split for economic reasons. The electrical signals from the plant 24 are converted into optical signals by electro-optic converters 28, 29. The optical signals are then transmitted on fiber-optic cables to a hub 30 which is located remotely from the plant 24. The optical signals are converted in the hub 30 back to the electrical signals by optic-electro converters 32, 34.

The switch 120 includes a first input port A having a switch 122 for switching between a first position as shown in solid line and a second position as shown in dashed line. A switch 127 is also provided at the output port. When switch 122 is in its solid line position so is switch 127. When switch 122 is in its dashed line position so is switch 127. When the switch 122 is in its solid line position, the primary channels from path 126 are operatively coupled to the output of the switch. When the switch 122 is in its dashed line position, port A is operatively coupled to a termination 130, for example, ground, preferably through a resistor 132.

The switch 120 also includes a second input port B having a switch 134 for switching between a first position shown in a solid line and a second position shown in a dashed line. When the switch 134 is in its second position, the backup channels from path 138 are operatively coupled to termination 140 preferably through a resistor 142. Switch 134 is in its solid line position when switches 122 and 127 are in their solid line position. When switches 122 and 127 are in their dashed line position so is switch 134. If switch 134 is in its dashed line position, the backup channels from path 138 are operatively coupled to the output port of the switch 120. The switches 122, 127 and 134 are arranged and configured such that they all switch simultaneously from their solid line position to their dashed line position and vice versa. Thus, when the switches are in their solid line positions, the primary channels are the selected signals and are coupled to the output of the switch and the backup or redundant channels are the unselected signals and are terminated. Conversely, when the switches are in their dashed line positions, the primary channels are the unselected signals and are terminated and the redundant channels are the selected signals and are coupled to the output of the switch.

The switch 120 also includes a controller 155 which controls the operation of the switch. More particularly, controller 155 controls the switching of switches 122, 127 and 134. In a preferred embodiment, controller 155 is a microprocessor programmed with software to control the operation of the switch as will be described in detail hereinafter.

Also shown in FIG.3, is a first detector 152 coupled to the output line of the switch. Detector 152 is used to monitor the condition of the selected signals. Accordingly, a failure, for example, a line cut, or a relay malfunction, etc., can be detected by the first detector 152. A second detector 154 is coupled to the termination 130 of the first switch 122 and the termination 140 of the second switch 138. The second detector 154 is used to monitor the condition of the unselected signals. This allows the users to know whether the backup signals on the redundant line are in a good condition or not. Preferably, the detectors 152, 154 are voltage detectors. If the condition of the backup signals maintains at a predetermined condition, the switch can switch to the backup signals when needed as will be described in detail with respect to the flowchart of FIG. 6. The second detector 154 monitors the terminations 130, 140 via a split coupler 158. The split coupler 158 may include couplers 160, 162, for example, resistors. Accordingly, the switch apparatus 120 provides a high level of isolation between ports A and B while allowing one detector, e.g. detector 154, to be shared between the two terminations 130,140. It is appreciated that one detector may be shared among more than two terminations within the scope of the principles of the present invention. It can be seen in FIG. 3 that the unselected line is terminated to ground through either resistor 132 or 142. This prevents unwanted reflections at the input port supplying the unselected signal.

The controller 155 is operatively coupled to the detectors 152, 154 and the switches 122, 127 and 134. The detectors 152, 154 monitor the condition of the selected and unselected lines, respectively. If the condition of the signal on the selected or unselected line exceeds a predetermined condition, preferably a threshold level, the detector generates a fault signal which is transmitted to the controller 155. In addition, the detectors 152, 154 are operatively coupled to an alarm 157, 159, respectively. The controller is programmed to switch the input of the switch from port A to port B if there is a failure on port A and port B is determined to be usable. If it is determined that port B also has a fault then the controller 155 will determine which is the best signal, the primary signal or the backup signal, and switch the switch accordingly. The operation of the controller 155 will be described in detail with reference to the flow chart of FIG. 6. When the detector 152 detects that the failed condition is over on the primary line, it alerts the controller 155 which switches the input back to port A. Preferably the controller introduces a delay before switching back to the primary to guard against temporary recoveries. The switch is preferably located in a housing indicated by the dashed line 120. For example, see U.S. Patent No. 5,963,842 assigned to the assignee of the present invention, for description of a housing. A communication port 160 is provided on the switch to allow a remotely located computing device to communicate with the switch through controller 155. As will be described in detail hereinafter. Preferably port 160 supports RS-485 protocol, however, other protocols may be used.

FIGS. 4a and 4b are a detailed diagram of the circuitry of a switch according to a preferred embodiment of the present invention. The switch is similar to that shown in FIG. 3 except that it has a second set of inputs and output as can be seen in the lower half of FIG. 4a.

FIG. 5 is a schematic view of a preferred embodiment of remotely controlled A/B switches according to the principles of the present invention. A controller 164, for example, a computer, is remotely coupled to a plurality of switches 120 that form a network environment. Preferably the controller 164 is coupled to the network by an Ethernet connection although the present invention is not limited to a particular type of connection.

As previously described, the controller 155 located in the switch, controls the operation of the switch. Thus, when the switches are in their solid line positions, the primary channels are the selected signals and are coupled to the output of the switch and the backup channels are the unselected signals and are terminated. Conversely, when the switches are in their dashed line positions, the primary channels are the unselected signals and are terminated and the redundant channels are the selected signals and are coupled to the output of the switch. If the condition of the signal reaches a predetermined condition, e.g. a failed condition (a failure in the transmission), then the detector sends a signal to the controller 155 which in turn sends a switching signal to the switches. When the detector detects the failed condition is over, the controller 155 sends a switching return signal to the switches. With reference to FIG. 5, the present invention allows the switches to be monitored, maintained and controlled by computer 164 remotely. Preferably software, stored on a medium such as a CD ROM is installed on the computer 164 which may be a personal computer or a server, for example. From the computer the user can monitor and control the entire network that is coupled to the computer. Preferably the computer communicates with he switches in the network over a RS- 485 bus. Alternatively, the computer can be coupled to the network over the Internet using TCP/IP protocol. Also, the computer may be provided with a SMTP email agent for pager notification if desired. As will be described in detail, from a remote location, a user, such as a network administrator, can view signal levels of the selected and unselected signals, set or modify switching threshold levels, set or modify the recalibration of a switch or a group of switches, as well as monitor and control all of the switches in the network. For example, the user can change the switch status of a switch or a group of switches remotely. In addition, the user can monitor alarm and failure statuses remotely. Because the user can change threshold settings, recalibrate switches and switch between channels all from a remote location, the need to dispatch a service person to the physical location of a switch is thereby eliminated. In addition, the user can download the new software to the controllers of the switches from the computer 164 as it becomes available. Preferably a graphic user interface is provided at the remote controller 164. FIG. 6 is a flow chart of the software resident on the controller of the switch shown in FIG. 3. There are basically four possible states for the switch: there can be no failed conditions on either the primary or backup signals; the backup signal may have failed but not the primary; the primary signal may have failed but not the backup; or both the primary and the backup may have failed. The flowchart of FIG. 6 illustrates the operation of the switch under all four scenarios as will now be described.

At block 600 power is applied to the switch. At decision block 602 it is determined whether the switch has passed a self-test. If it has not, control is passed to block 604 where a failure is indicated. For example, a signal may be sent to the remote computer coupled to the switch to alert a network administrator. If it is determined at block 602 that the switch passed its self-test, then at block 606 the previous state of the switch is recalled. Depending on the recalled state of the switch, control will be passed to various blocks. For example, if the recalled state is that the switch has not been calibrated, control is passed to block 608. If it is recalled that there has been no failure, control is passed to block 610. If the recalled state is that the backup channel had a failure, control is passed to block 624. If the recalled state is that there has been a failure on both the primary and redundant channels, control is passed to block 634. The operation implemented by the flow chart will now be described beginning at decision block 608. At block 608 it is determined whether the switch has been calibrated. The switch can be calibrated either remotely using the computer or, it can be done locally at the switch. Assuming that the switch has been calibrated and there have been no failures, then at block 610, the selected and unselected detectors measure their respective voltages and add them to a running average. Control is then passed to block 612 where the running average is converted to a signal power measurement. At decision block 614 it is determined whether either the primary or the backup channel has failed. If neither channel has failed, then at block 616 it is determined whether the delay timer has expired, if the delay timer has been previously set in block 632. If the timer had not been set or if it has expired, then at block 618, a control signal to switch the switches to the primary channel is generated if the backup path was the current selected signal. If the delay timer had been set and had not expired as determined at block 616, control is returned to block 610. This prevents a switch to the primary channel from the backup channel from occurring until enough time has elapsed. If it was determined at block 614 that either the primary or backup channel has failed, control is passed to decision block 620 where it is determined if it was the selected signal. If it was, then at block 622 the switch is commanded to switch to the other, non-active channel or unselected signal. A switch is made in this circumstance because it is known from the recalled previous state that there was no failure in the unselected signal path. If, however, it is determined at block 620 that the active or selected side had not failed, no switching to the redundant, i.e., backup, unselected or non-active, signal would occur.

Once the switch in block 622 has been made, preferably the backup channel is being used. Because the backup channel generally is not as good as the primary channel, it is desirable to switch back to the primary as soon as possible. At blocks 624, 626, the detector measurements are made and converted as previously described. Then, at decision block 628, it is determined if the backup channel which is now the active channel has failed. If it has not, then at decision block 630, it is determined whether the primary channel which is now the non-active signal is good meaning the failed condition has been eliminated. If it has not, the backup channel remains the active or selected signal and control is returned to block 624. If the primary channel is good as determined at block 630, then a delay timer is set at block 632 and control is returned to block 610. The switch to the primary channel will then be made once the timer has expired as previously described.

If it is was determined at decision block 628 that the backup channel failed, now both the primary and backup channels have failed. In such a situation, the controller decides which of the failed signals is the best. Again at blocks 634, 636, the detector measurements are made and converted. At block 638 a switch from the backup channel to the primary channel will be made if it is stronger than the backup channel. At decision block 640, it is determined whether either channel is good. If not, control returns to block 634. If a failed condition has been eliminated then control is returned to step 624.

It is appreciated that the switch apparatus 120 can be implemented in an amplifier switch, a dual A/B switch, a split linked A/B switch, etc. It is also appreciated that the communication between the computer and switching equipment can occur on RS-485, or RS-485 in combinations with Ethernet, etc. Further, it is appreciated that the remote control can be provided with a graphic user interface on a computer.

FIG. 7 is a flowchart of the software used to control a split signal A/B type switch. It can be seen that the flow chart is almost identical to that shown in FIG. 6 however, blocks 722, 728, 730 and 740 are modified to reflect the fact that the primaiy channels are split. The split signal A/B switch is comprised of two A/B switches and is designed for specific applications where the signal is split into a group of lower channels (i.e. ch 2-49) and a group of upper channels (i.e. ch 50- 100). For example, a CATV signal split onto two 13 lOnm fiber-optic transmission lines to improve signal quality. Each group is independently monitored, however if a failure occurs in either group, both groups are switched simultaneously to the back-up channel. The back-up channel can also be split into two groups or may contain all channels on one single signal bath, using a 1550nm fiber-optic transmission system.

FIG. 8 is a schematic of a redundant amplifier switch 800. The redundant amplifier switch provides protection of CATV head-end amplifiers as opposed to signal paths as with the switches previously described. This switch 800 monitors the gain of amplifier 802 and upon detection of a failure, a standby amplifier 804 is powered up and immediately switched in to replace the failed amplifier 802. The main and backup amplifiers 802 and 804 are operatively coupled to the switch controller 806 which monitors the status of each amplifier. As will be described in detail, if it is determined that both amplifiers have failed, then the controller switches momentarily back to the currently unselected amplifier and then determines which amplifier has overall the best gain and switches to that amplifier. FIG. 9 is a flowchart of the software used to control the redundant amplifier switch. At block 900 power is applied to the switch. At decision block 902 it is determined whether the switch has passed a self-test. If it has not, control is passed to block 904 where a failure is indicated. For example, a signal may be sent to the remote computer coupled to the switch to alert a network administrator. If it is determined at block 902 that the switch passed its self-test, then at block 906 the previous state of the switch is recalled. Depending on the recalled state of the switch, control will be passed to various blocks. For example, if the recalled state is that the switch has not been calibrated, control is passed to block 910. If it is recalled that there has been no failure, control is passed to block 912. If the recalled state is that the backup channel had a failure, control is passed to block 926. If the recalled state is that there has been a failure on both the primary and redundant channels, control is passed to block 940. The operation implemented by the flow chart will now be described beginning at decision block 910. At block 910 it is determined whether the switch has been calibrated. The switch can be calibrated either remotely using the computer or, it can be done locally at the switch. Assuming that the switch has been calibrated and there have been no failures, then at block 912, the selected and unselected detectors measure their respective voltages and add them to a running average. Control is then passed to block 914 where the running average is converted to a signal power measurement. At decision block 916 it is determined whether the input signal is too low, i.e., too weak. If it is, control is passed to block 950 which will be described hereinafter. If it is determined that the input signal is not too weak, then at back 920 the gain of the amplifier 802 is calculated. AT block 922 it is determined based on the gain calculated in block 920 whether amplifier 802 has failed. If it has not, control is returned to block 912. If it was determined that amplifier 802 failed, then at block 924 the input is switched to the backup channel with amplifier 804. The same steps as described at blocks 912- 924 are again performed at blocks 926-938 for the backup channel. If a switch is made at block 938 indicating that both the primary and backup channels have failed, then at block 940 the power of the input signal is measured and at block 942 the input is switched to the other channel and at block 944 its power is measured. At block 946 the measurements made at blocks 940 and 946 are compared and the input that is the strongest is selected. Finally, at block 948 it is determined whether the switch has been calibrated. If it has, control is passed to block 912. If it has not been calibrated, control is returned to block 948 and remains there until the switch is calibrated. If it was determined either at block 916 or block 930 the input signal was too low, then at block 950 it is determined if the input signal is no longer weak, i.e., is it now good. If it is, then control is returned to the block where the loss of signal was detected.

FIG. 10 is a flow chart of the detection software resident on the controller of a switch according to a preferred embodiment of the present invention. First at block 1102 the input signal is measured and stored in a memory of the switch as a before value. At block 1104 the controller switches the input and at block 1106 the input signal is measured after the switch and stored as a after value. At block 1108 it is determined whether the after signal is approximately equal to the before signal. If it is, the switch was a good switch and the routine is ended. If not, at block 11 10 an indication that the switch has failed is generated. This indication is preferably transmitted to the remote computer for display to a user either immediately or at a later time, for example, perhaps in an even log.

FIG. 11 is a flow chart of the communication and control software between the remote controller and the network environment. First at block 1200 a message from the remote controller is received by each switch in the network coupled to the remote controller. At block 1202 it is determined whether the message is complete. If it is not, control is returned to block 1200. If it is, then at block 1204 it is determined by the switch if it is the intended recipient of the message. If it is not, control is returned to block 1200. If it is, then at block 1206 the message is parsed by the switch and at block 1208, the switch performs the action dictated by the message, and, if appropriate, transmits a message back to the remote controller. For example, the message from the remote controller may be to change a threshold level. The controller to the switch receives, the message, changes the threshold level and transmits a message back to the remote controller that the change has been made. FIG. 12 is a screen shot displayed at the remote controller according to a preferred embodiment of the present invention. The screen shot provides important information to a user such as an administrator of the network about the network and allows the user to change and control aspects of the network. The screen is divided into three sections. In the first section 1000 shown on the left side is a tree-like listing of the network environment coupled to that remote controller. In the particular example shown, the environment is the Twin Cities. A plurality of regions are listed and each region can be expanded by clicking on the plus sign located adjacent to the region. In the example shown, the "South West" region has been selected which is shown to be further divided into an Eden Prairie East and West subregion. The Eden Prairie West region has been selected to illustrate all of the switches 1004 located in the subregion. In this example t her are eight switches. Located adjacent to each switch is a first indicator 1006 and a second indicator 1008. The first indicator 1006 shows the status of the primary channel signal of the switch and the second indicator 1008 shows the status of the backup signal of the switch. If there are no failures both indicators are colored green. If a failure is detected the indicator of the failed signal turns red. Thus, the user can easily see the status of the switch. In addition, indicators are also provided adjacent to the regions and subregions and those indicators will turn red whenever any switch in the particular region or subregion fails.

A second section 1010 of the screen displays a log of events that have occurred on the network. For example, events such as when a switch was made, when was a switch recalibrated, when was a loss of signal detected. Also, warnings and failures such as under or over threshold warnings are logged. It is useful to provide over threshold warning which indicate that the input signal is too strong and may damage the circuitry in the sets that are receiving the input signal.

The third section 1012 of the screen provides the user with detailed information concerning a particular switch, in this case switch South 1. Graph 1020 illustrates various information about port A of the switch. A bar graph 1022 is colored red to indicate that there is a failure on the signal input to port A. The height of the bar graph reflects the strength of the signal. Since the height is low, the signal strength is low. The current over and under threshold values are displayed at 1024 and 1026 respectively. The user can change these values using the buttons adjacent to he display. A recalibrate button is shown grayed out for port A since a port can not be recalibrated if there is a failure at that port. Graph 1030 illustrates various information about port B of the switch. A bar graph 1032 is colored green to show that the backup signal is good. The height of the bar graph indicates that the strength of the signal is strong. Over and under threshold values are displayed and the user can change those values. In addition, because the backup signal is good, that port can be recalibrated using button 1034. A switch button 1036 is shown grayed out thereby preventing the user form switching back to port A while there is still a failure at that port. Once the failure has cleared and preferably after a prescribed delay period, the switch button 1036 will be active so that the user can make a switch. Also indicated in this section of the screen is the serial number 1040 of the switch, a description 1042 of the switches location and connections and a failure history 1044 for that switch. FIG. 13 is an alternate preferred embodiment of an A B switch according to the present invention. It can be seen that in comparison to the switch shown in FIG. 3, three detectors are now used instead of two. Each input port and the output port are coupled to the detectors. The non-active port is still terminated. The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.

Claims

What is claimed is:

1. A switch comprising: a first input port; a second input port; an output port wherein when the switch is in a first position, the first input port is coupled to the output port to define a selected signal path and the second input port defines an unselected signal path and when the switch is in a second position, the second input port is coupled to the output port to define a selected signal path and the first input port defines an unselected signal path; a first detector coupled to the selected signal path through which a selected signal will flow to monitor the selected signal; and a second detector coupled to the unselected signal path through which an unselected signal will flow to monitor the unselected signal.

2. The switch according to claim 1 wherein when the switch is in the first position, the second input port is terminated and when the switch is in the second position, the first input port is terminated.

3. The switch according to claim 1 wherein the first detector is operatively coupled to the output port and the second detector is operatively coupled to either one of the first or second input port.

4. A switch apparatus, comprising: a first switch switching between a first position which operatively couples a first input to an output to define a selected signal path and a second position which operatively couples the first input to a termination to define an unselected signal path; a second switch switching between a first position which operatively couples a second input to the output to define a selected signal path and a second position which operatively couples the second input to the termination to provide an unselected signal path wherein when the first switch is in its first portion, the second switch is in its second position and whether the first switch is in its second position, the second switch is in its first position; a first detector for continuously monitoring the selected signal; and a second detector for continuously monitoring the unselected signal.

5. The switch apparatus of claim 4, wherein when the condition of the selected signals reaches a predetermined condition, and the condition of the unselected signals remains at a predetermined condition, the first switch is switched from its first position to its second position and the second switch is switched from its second position to its first position so that the unselected signals become the selected signals, and the selected signals become unselected signals.

6. The switch apparatus of claim 4, wherein when the condition of the selected signals reaches a predetermined condition, the first switch is switched from its first position to its second position and the second switch is switched from its second position to its first, so that the unselected signals become selected signals, and the selected signals become unselected signals.

7. The switch apparatus of claim 4 wherein the first detector is operatively coupled to the output.

8. The switch apparatus of claim4, further comprising a controller located external to the switch apparatus wherein the controller is operatively coupled to the switch apparatus for remotely controlling the switch apparatus.

9. The switch apparatus of claim 5, wherein when the predetermined condition of the selected signals is no longer detected, the first and second switches are switched back after a predetermined period of time.

10. The switch apparatus of claim 6, wherein when the predetermined condition of the selected signals is no longer detected, the first and second switches are switched back after a predetermined period of time.

11. The switch apparatus of claim 4, wherein an amplitude of each of the output signal is measured before and after each switch action.

12. The switch apparatus of claim 4, further comprising a controller located external to the switch apparatus wherein the controller is operatively coupled to the switch apparatus for remotely monitoring the switch apparatus.

13. A method of providing reliable switching in a switch, the method comprising the steps of:

(a) providing a selected signal path through the switch;

(b) providing an unselected signal path through the switch; (c) simultaneously monitoring the selected signal path and the unselected signal path.

14. The method of claim 13 further comprising the step (d) of continuously monitoring the selected signal path and the unselected signal path.

15. The method of claim 13 further comprising the step (d) of generating an alarm if either the selected or unselected signal path exceeds a predetermined condition.

16. The method of claim 13 wherein step (c) is performed remotely from the switch.

17. The method of claim 13 further comprising the step (d) of switching from the selected signal path to the unselected signal path if the selected signal path experiences a failure.

18. The method of claim 17 further comprising the step of (e) determining the reliability of the unselected signal path before step (d).

19. The method of claim 13 wherein if it is determined in step (c) that the selected and unselected signal paths have experienced a failure, the method further comprising the step (d) of determining which of the signal paths is strongest and switching to that signal path.

20. A computer-readable medium having computer-executable instructions for the method recited in claim 13.

21. A computer data signal embodied in a carrier wave readable by a computing system and encoding a computer program of instructions for executing a computer process performing the method recited in claim 13.

22. A method of remotely controlling a switch, the method comprising the steps of: (a) generating a graphical user interface on a computing device located externally and remotely from a switch;

(b) determining what switch is operatively coupled to the computing device; (c) displaying status information concerning both a selected signal and an unselected signal of the switch operatively coupled to the computing device on a display.

23. The method of claim 22 further comprising the step of displaying a threshold level that the switch is set at for both the selected and unselected signals.

24. A system for remotely monitoring and controlling a network of switches, the system comprising: a general purpose computing device operatively coupled to the network; a computer program comprising one or more program modules executable by the computing device wherein the program modules comprise a network topology module for generating a display at the computing device of the topology of the network, a user interface module for interpreting inputs provided by a user, a network interface module for transmitting messages to the network and receiving messages from the network.

25. A method of switching between a first line of signals coupled to a first switch and a second line of signals coupled to a second switch, comprising: connecting a third switch to the first switch such that the first line of signals are selected and sent to an output line coupled to the third switch, and the second line of signals are unselected and terminated at a termination of the second switch; and monitoring a condition of the selected first line of signals and a condition of the unselected second line of signals: when the condition of the selected first line of signals reaches a predetermined condition, and the condition of the unselected second line of the signals maintains at a predetermined condition, the third switch is switched to connect to the second switch such that the second line of signals are selected and sent to the output line coupled to the third switch, and the first line of signals are unselected and terminated at a termination of the first switch.

26. A method of switching between a first line of signals coupled to a first switch and a second line of signals coupled to a second switch, comprising: connecting a third switch to the first switch such that the first line of signals are selected and sent to an output line coupled to the third switch, and the second line of signals are unselected and terminated at a termination of the second switch; and monitoring a condition of the selected first line of signals: when the condition of the selected first line of signals reaches a predetermined condition, the third switch is switched to connect to the second switch such that the second line of signals are selected and sent to the output line coupled to the third switch, and the first line of signals are unselected and terminated at a termination of the first switch.