WO1999065208A2

WO1999065208A2 - Signal monitoring and automatic line cut-off apparatus on a telephone line

Info

Publication number: WO1999065208A2
Application number: PCT/KR1999/000287
Authority: WO
Inventors: Chong Tai Kim; Gi Hong Kim; James Jimin Kim
Original assignee: Chong Tai Kim; Gi Hong Kim; James Jimin Kim
Priority date: 1998-06-11
Filing date: 1999-06-10
Publication date: 1999-12-16
Also published as: AU4291799A; WO1999065208A3

Abstract

In a communication system in which both voice signal generating devices such as telephone and data signal generating devices such as fax and modems share and are coupled to the same telephone lines, a monitoring and indicating apparatus is provided which determines whether the line is being used and what type of device is being used thereby to prevent other terminal devices accidentally from disturbing the ongoing communication. The apparatus comprises a data signal detector for detecting a data signal along the telephone line, a voice signal detector connected to the telephone lines in parallel with the data signal detector for detecting whether the telephone line is in use, a display and indicator including a voice signal indicator connected to the voice signal detector which is activated along when the telephone line is being used and a data signal indicator connected to the data signal detector which is activated when the telephone line is being used for data communication, and a cut-off device which is located in between the telephone line and the additional communication device which opens to prevent the telephone from disturbing the data communication when both the voice signal detector and the data signal detector indicate that the line is used for data communication.

Description

SIGNAL MONITORING AND AUTOMATIC LINE CUT-OFF APPARATUS ON A TELEPHONE LINE

Background of the Invention

1. Field of the Invention

This invention generally relates to a new telephone line monitoring apparatus, more particularly to a telephone line monitoring apparatus used in conjunction with telephone sets or communication devices which are connected in parallel to a telephone line wherein the line is shared among the devices. This invented apparatus detects the types of signals on the telephone line and displays these on it so that other callers connected to the same line may be aware that the line is already being used. This invention also minimizes interruptions by other users by providing an automatic line cut-off capability when the line is already being used by someone else.

?. Description of the Prior Art

Many family houses or small offices are served by only one telephone line which is shared among many telephone sets, fax machines and computers. The sharing devices are all connected to the line in parallel. Sometimes more than one line are used, but all communication devices are connected to the line in parallel.

The most currently available single-line telephone sets and communication devices have no indicator that displays whether the line is already being used by someone else. And if the line is being used, there is no indication for what the line is being used. For example, there is no way of telling whether the line is being used for voice communication or for data communication.

Problems arise when someone tries to use the line (either to make a telephone call, send a fax or to connect to the internet) while the line is already being used by someone else. Since there is no way of knowing without picking up the handset whether the line is being used, the new caller tries to make a call by simply lifting the handset. This creates an interruption for the other caller who is already using the line. For the voice application, this interruption does not affect the call in progress although it may be an annoyance to or may invade the privacy of the other user. The new caller upon hearing the voice conversation, simply places the handset back. But when the line is used for data communication

(for example, fax or modem) , the entire communication may be interrupted and the connection may be dropped.

Therefore, it is recognized that there exists a need for a signal monitoring and automatic on-hook apparatus which can be used to alert a new caller by indicating that the line is already being used by someone else and for what type of communication it is being used for. This would prevent an interruption of the fax or modem communication in progress when the new caller tries to use the line accidentally. The present invention substantially fulfills this need.

In general, there have been prior developments for signal detection on a telephone line, as described in U. S. Patent No. 5,018,190 by Walker, et al, that was issued on May 21, 1991. This prior art allows the detection of a modem call on a PBX line and responding to it by hanging up or connecting to a switch to allow the call to pass. The circuits making up the prior art, namely, data signal detectors are commonly available in the market. In many cases, such devices have already been integrated into communication equipments. But there never has existed an apparatus that detects voice or data, in addition to whether the line is being used or not, and displays it on the apparatus. Also, there never existed an apparatus which makes the communication devices connected to it automatically cut off when the user tries to use the line if the line is already being used.

Summary of the Invention

The present invention provides a new communication status detection and automatic on-hook device to prevent another caller from using the line when the line is already being used by someone else. One aspect of the invention is to detect the type of communication and display it on the invented device. In general, there are two different applications for telephone lines being used today: voice and data. Indicators in the invented apparatus show whether the line is being used for voice communication or for data communication. When the line is used for voice communication, a voice indicator would be "on" but a Fax/Modem indicator would be "off", while when the line is used for fax or data communication, the fax/modem indicator and the voice indicator both would be "on".

When the line is not being used, both indicators would be "off".

A commercial application of the invention is integration of this invention into communication products to alert the user to prevent unexpected interruptions by other devices sharing the same line. This design, in a form of a stand-alone device or as an imbedded part of the telephone set or communication devices (for example fax machine and modem terminal) , will also monitor the use of the network time. A practical example is for internet use of the telephone line. Numbers of the internet users are increasing and the network usage time for internet will drastically increase in the next few years. The current trend also indicates that school-age children will use the internet as much time as watching TV. This creates much concern for the parents. Sometimes, the children use the internet for several hours a day and this becomes a serious problem to other members of the family who share one telephone line. The parents do not know whether the line is being used by the children for internet and if it is being used, there is no way for the parents to know how long the line is being used.

This invention provides a tool for the parents to monitor the line usage as well as alerting other callers that the line is already being used.

This invention makes it possible to monitor the types of communication use and duration of the use for a telephone line and display it on the device. The above outline describes, rather broadly, the more important features of this invention in order that the detailed description that follows herein may be better understood and that the present contribution to the art may be better appreciated. In this respect, before explaining at least one embodiment of the invention in detail it is to be understood that the invention is not limited in its application to the particular details of construction and to the arrangements of the components set forth in the following description and illustrated in the drawings. The invention can also be added to other communication devices in various ways if it has its own communication protocol. For an example, in a new communication device with a new communication format introduced late, the new detection scheme can be added to this invented apparatus and a new indicator would be added to indicate that new type of communication. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception and the detailed design, upon which this disclosure is based, may readily be utilized as a basis for designing other devices for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent realizations insofar as they do not depart from the spirit and scope of this invention. Therefore, an objective of the present invention is to provide a new detecting device for a telephone line which has all the advantages of the prior art detectors of various designs and configurations without their disadvantages . Another objective of the present invention is to allow detection of telephone line signals and display of the information by way of a stand-alone device or a device embedded in the telephone, fax machine, modem or other communication equipments which can be easily and efficiently manufactured and marketed.

It is a further objective of the present invention to provide a capability of monitoring the use of the phone line which is a growing concern within a household.

Brief Description of the Drawings

The above and other objects, features and advantages of the invention will become apparent from a reading of the following detailed description, when considered with the accompanying drawings, wherein: Figure 1 is a diagram of a typical household or an office showing how the communication devices are connected to a telephone line;

Figure 2 illustrates how the invented apparatuses are connected to the line;

Figure 3 is a block diagram of the invented apparatus;

Figure 4 is a block diagram of the invented apparatus with the cut-off (on-hook) feature when the data communication is used on the line;

Figure 5 is a block diagram of the invented apparatus with the cut-off feature when the voice communication is used on the line;

Figure 6 is a block diagram of the invented apparatus with the cut-off feature indicating whether the line is being used for voice communication or data communication;

Figure 7 is a block diagram of the invented apparatus integrated into a communication device; and, Figure 8 is a diagram of a telephone set with the apparatus built-in.

Detailed Description of the Preferred Embodiments

This invention applies to a signal monitoring apparatus for a telephone line which allows monitoring the line usage and status while the line is used for communication. This invented apparatus is connected to a telephone line in parallel the same as other communication devices. When a device connected to the telephone line is used either for voice communication or for data communication, the invented apparatus detects the types of signal, displays it and disconnects the other communication devices connected to the line to prevent another user from accidentally interrupting the communication by the user who is already using the line.

The figure 1 shows how the communication devices are connected to a telephone line in a typical household or an office. All communication devices are connected to the line in parallel.

The figure 2 shows how this apparatus according to the present invention is connected to a telephone line. The reference numeral 1 indicates the invented apparatus connected to a telephone line. The same as other communication devices, the apparatus is connected to the line in parallel. The invented apparatus can be implemented in stand-alone manner.

As shown in figure 3, this apparatus comprises: a) a data signal detector including an AC differential amplifier (21) which is connected to the telephone line in parallel and which blocks DC signal components and allows only AC signals to pass, a bandpass filter (22) which filters out the signal components that reside outside of the frequency spectrum of interest, an envelop detector (23) which detects the peaks of the rectified full-wave form, a threshold level detector (25) which compares the enveloped voltage level with a reference voltage level, and a duration time detector (26) which moves a sliding timing window and examines the voltage level to produce a high or low state while the voltage level is compared with the reference, thus, producing an output of the signal detection; b) a voice signal detector including a bridge diode (28) which prevents the polarity reversal of the tip (10) and the ring (11) lines and a parallel off-hook detector (27) which detects the off-hook signal state on the telephone line; and c) display and indicator including an AND gate (29) which produces a high state when both the data signal detector and the voice signal detector states are high, a voice communication indicator

(41) which indicates whether the line signal is a voice signal, and a data communication indicator

(42) which indicates whether the line signal is a data communication signal such as a fax or modem communication.

The blocks from the AC differential amplifier (21) through the duration time detector (26) in figure 3 represent the signal detector for the data communication. The blocks from the bridge diode (28) through the voice communication indicator (42) represent the off-hook detector and the detection of the voice communication.

When a communication device connected to the phone line initiates a call or receives a call for communication, the invented device would signify an "off- hook" state.

The voltage level on the tip line (10) and the ring line (11) changes from -48 volts DC to approximately -5 volt DC when the line is seized by a device connected to the line and a connection is made between the sender and the receiver. When the connection is made by data devices, the data devices at both ends initiate the communication protocol by generating AC hand-shake signals. These AC signals are exchanged between the devices during the data communication all along. As shown in figure 3, when AC signals are transmitted or received, the AC differential amplifier (21) picks up and amplifies the AC signal components and sends them to the bandpass filter (22) . A high input impedance is used to minimize effects on communication by other devices on the telephone line.

The bandpass filter (22) filters out the AC signals and passes signals which are only in a specified frequency band to the envelop detector (23) . The bandpass filter (22) is used to eliminate the signals that are out of the band specified for data communication.

The envelop detector (23) verifies the incoming AC signals and convert them to a DC level by only taking the peak voltage values. If this voltage level is lower than the reference voltage level (24), then the threshold level detector (25) produces a low-state signal output (level "0") . If the output of the envelop detector (23) DC voltage level is greater than the reference voltage level (24), then the threshold level detector (25) produces a high-state signal output.

The reference voltage level (24) can be set depending on the communication devices sharing the line. The reference voltage level is determined by the minimum communication signal level used by the communication device.

The duration time detector (26) measures the duration of the input signal. If the input signal level to the threshold level detector (25) is high state (for example "1") and the level is maintained for a predetermined duration window (for example, 10 seconds) , the duration time detector (26) produces a high state output of "1" and is indicative of usage of the telephone line by a data communication device. If the input signal level of the threshold level detector (25) is the high state of "1", but the level is not maintained for the predetermined duration, the time duration detector produces a low state output of "0". This process is continuously repeated during the entire operation. The output of the time duration detector (26) constitutes the output of the signal detection and is passed to the AND gate (29) . For monitoring of the line usage, different duration windows are established with different indicators associated to signify the different levels of line usage.

A bridged diode (28) is used to prevent the polarity reversal problem of the tip (10) and the ring (11) lines. When a communication device sharing the line becomes off-hook state, the voltage level of the telephone line drops down to approximately -5V DC. The parallel off-hook detector (27) detects the off-hook state by detecting the voltage change on the line and produces a high-state signal output of "1".

When the output of the voice signal detector is the high state ("1"), the voice communication indicator (41) is turned on.

For example, when a LED is used as the indicator, the LED light is turned on. This indicator stays on until the communication device becomes "on-hook". When the communication device becomes "on-hook" state, the output of the off-hook detector becomes the low state ("0") and the voice communication indicator is turned off. This indicator represents the voice communication on the line. The off-hook detector output also becomes an input to the AND gate (29) .

The AND gate (29) receives input level from the parallel off-hook detector (27) and the duration time detector (26) . When the input level from the parallel off-hook detector (27) is high state ("1") and the input level from the duration time detector (26) is also high state ("1"), then the data communication indicator (42) is turned on. Otherwise, the data communication indicator remains off.

Along with the voice communication indicator (41), the combination of these two indicators indicates two different modes of communication.

When the voice communication indicator (41) is on and the data communication indicator (42) is also on, it signifies that the data communication is being conducted on the telephone line. When the voice communication indicator (41) is on but the data communication indicator (42) is not on, then it signifies that the voice communication is being conducted on the telephone line. Both indicators or the voice indicator remain on as long as the communication is progressing on the telephone line.

Fig. 4 shows an automatic cut-off circuit for preventing the interruption of the communication. As shown in figure 4, the automatic cut-off scheme

("on-hook" feature) prevents the interruption of the data communication when a new caller tries to use the line accidentally. While someone is using the line, when another user tries to use one of the other communication devices on the same line, the communication device has already become "on-hook" state. These devices remain "on- hook" state as long as the current active device remains off-hook state.

The automatic cut-off circuit includes a serial off- hook detector (30) which detects the loop current flowing at the line serially connected to the communication device, a cut-off AND gate (31) which receives the signals from the AND gate (29) and from the serial off- hook detector (30), a switch (33) which opens and closes the telephone line, and a switch controller (32) which controls the switch. When the communication device becomes "off-hook" state, the loop current flows and the serial off-hook detector (30) produces a high-state signal output. If the device is not used, the serial off- hook detector (30) is at low-state. Optical photo devices are used in the serial off-hook detector (30) to minimize any effects on communication. A signal is generated by the cut-off AND gate (31) depending on the signal levels of the serial off-hook detector (30) and the AND gate (29) .

The tip (10) and ring (11) lines with cut-off feature are connected to a communication device or a telephone set (35) in serial. When a person is trying to use the line, the serial off-hook detector (30) detects the off-hook signal and sends a high-state signal to the cut-off AND gate (31). The AND gate (29), the output from the signal detector, is also connected to the cut-off AND gate (31) . When the line is being used for data communication, it sends a high-state signal ("1") to the data communication indicator (42) and the same signal is also being sent to the cut-off AND gate (31) .

When the cut-off AND gate (31) receives a high-state signal from the AND gate (29) and a low-state signal from the serial off-hook detector (30) , the cut-off AND gate (31) produces a high-state signal output and sends it to the switch controller (32) to open the switch (33) of the line. Otherwise, the switch remains closed. Anyone who lifted the handset before the line is cut off will be stayed in an off-hook state regardless of data signal detected thereafter.

The automatic cut-off scheme (on-hook feature) for the voice communication is shown in figure 5. The output of the parallel off-hook detector (27) which indicates that voice communication is in progress is connected to the cut-off AND gate (31) . When the cut-off AND gate (31) receives a high-state signal from the parallel off-hook detector (27) and a low-state signal from the serial off- hook detector (30) , it produces a high-state signal output. The switch (33) opens the line and cut off the other line-sharing communication devices (35) when the voice communication is being already used in the line. In this application, the signal detection scheme may not be implemented.

The automatic cut-off scheme (on-hook feature) for data communication and voice communication is shown in figure 6. The outputs from the parallel off-hook detector (27) and the output of the AND gate (29) are connected to the OR gate (34) and the output of the OR gate (34) is connected to the cut-off AND gate (31) . The other line- sharing communication device (35) will be cut off when either voice communication or data communication is in progress on the line. The figure 7 is a connection diagram for a communication device and the invented apparatus which is integrated to a communication device.

The figure 8 is a design of the telephone set into which the apparatus is integrated. Those skilled in the art will readily recognize that these and various other modifications and changes may be made to the present invention without strictly following the exemplary application illustrated and described herein and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.

Claims

What is claimed is:

1. In a communication system including tip and ring telephone lines and at least one or more voice signal generating devices and data signal generating devices sharing and coupled to the telephone line, a monitoring and indicating apparatus for determining whether the line is being used and what type communication devices is being used, comprising: a data signal detector for detecting a data signal along the telephone line; a voice signal detector including a bridge diode for preventing the polarity reversal of the tip and ring telephone lines and a parallel off-hook detector connected to the telephone line in parallel with the data signal detector for detecting the off-hook signal state on the telephone line; and, a display and indicator including an AND gate coupled to the data signal detector and the voice signal detector, the AND gate producing a high state when both the data signal detector and the voice signal detector states are high, a voice communication indicator connected to the off-hook detector which is activated alone when the telephone line is being used, but not for data signal generation, and a data communication indicator connected to the AND gate which is activated along with the voice signal indicator when the telephone line is being used for data signal generation.

2. The invention defined by claim 1, wherein the data signal detector comprises: an AC differential amplifier connected to the telephone line in parallel, the AC differential amplifier for blocking DC signal components and passing only AC differential signals, on the tip and ring lines when the communication devices become off-hook state and voice or data communication signals are being produced or received; a bandpass filter having an input connected to the AC differential means for filtering out signal components that are outside of a specified frequency band; an envelop detector having an input connected to the bandpass filter for detecting peaks of rectified full- wave form; a threshold level detector which receives the input from the envelop detector, compares the enveloped voltage level with a reference voltage level and produces a high- state signal (level "1") or a low-state signal (level "0") ; and, a duration time detector having an input connected to the threshold level detector, the duration time detector producing an output according to the duration of the high-state signal level.

3. The invention defined by claim 1, wherein the bridge diode is placed in series between the telephone lines and the off-hook detector to prevent the telephone line polarity reversal.

4. The invention defined by claim 1, including means for automatically cutting off a signal generating device sharing the telephone lines but not currently being used, the automatic cut-off means comprising: a serial off-hook detector connected in series between the telephone lines and the unused signal generating device, the off-hook detector producing a high-state signal output when the telephone line is in an off-hook mode; a cut-off AND gate for receiving signals from the AND gate and from the off-hook detector and the input to a communication indicator and for producing a control signal when an input from a communicator indication input is in a high state and the input from the off-hook detector is in a low state; a switch arranged in series between the off-hook detector and the unused signal generating device, which opens and closes connecting between the unused devices and the telephone lines; and, a switch controller for controlling the switch depending on the output level of the cut-off AND gate.