JPH02268057A - Monitor system for 2-wire television interphone system - Google Patents

Abstract

PURPOSE:To obtain a 2-wire TV interphone system processed for multi-station facility by providing a relay adaptor between a master set and a slave set, incorporating a master set operation sensing section, a master set selection section, a dummy load and a changeover section and providing a monitor operation means to the master set. CONSTITUTION:A relay adaptor 22 is provided between plural master sets 4 and plural slave sets 1. An adaptor uses a master set operation sensing section 26 to detect an operating voltage from a master set to a slave set to sense the operation of the master set and the sensing output starts a master set selection section 25 to select the master set thereby supplying the voltage in the operation from the master set to the slave set. A changeover section 32 connects the master and a dummy load 31 and the voltage in the operation from the master set to the slave set is absorbed by the dummy load 31. A monitor operation means 40 of the master set 4 is in operation, the voltage is outputted optionally. When an output comes from an all-master set operation sensing section 26 within a prescribed time, the master is started at the call of the slave set and in the presence of an output of the sensing section 26 corresponding to part of the master set, it is discriminated as a monitor signal, and the voltage in the operation from the master set corresponding to the sensing section 26 outputted at first is outputted to the slave set and the remaining master sets are connected to the dummy load 31 via the changeover section 32 to form the 2-wire TV interphone system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a monitoring method for a two-wire television intercom system that is designed to have multiple stations.

[Conventional technology] In order to make it possible to see guests indoors, a monitor TV camera is installed on the handset installed at the entrance, and a TV monitor is installed on the base unit installed indoors to allow calls. At the same time, a television intercom system capable of displaying images captured by a monitor television camera was developed and began to be used.

As shown in FIG. 3, in such a TV intercom system, when a call button 2 of a handset 1 installed at a doorway is operated, a base unit 4 installed indoors is called through a transmission line 3.
A ring signal is transmitted to the base unit 4, a ring tone is output from the speaker 5 provided in the base unit 4, power is supplied to the monitor TV camera 6 of the slave unit 1, and the video signal of the monitor TV camera 6 is transmitted to the base unit 4. The information is sent to the base unit 4 through the transmission line 3 and displayed as an image on the monitor television 7, and when the resident picks up the handset 8 and answers the call, the user can make a call.

FIG. 4 shows a circuit block of the TV intercom system shown in FIG. The base unit 4 and the slave unit 1 are both connected to the transmission line 3.
The base unit 4 supplies power to the slave unit 1 side through the transmission line 3, and the video signal from the monitor TV camera 6, the call signal, or the connection between the base unit 4 and the slave unit Necessary information can be communicated by multiplexing and transmitting voice signals of one call.

More specifically, the base device 4 includes a power superimposing circuit 9 for supplying power to the handset 1, a modulation section 10 that modulates a high-frequency signal using a call voice signal from the handset 8, and a modulation section 10 for modulating a high-frequency signal using a voice signal sent from the handset 1. A demodulating section 11 demodulates the modulated signal and extracts a call audio signal, and a video signal receiving section 12 receives the video signal sent from the handset 1 and outputs it to the monitor television 7. a call detection section 13 that receives a call signal sent out by the circuit group and generates a speaker ringing signal; and a balancing section that is interposed between the circuit group and the transmission line 3 and balances unbalanced signals of the circuit group. The circuit 14 and the short circuit protection circuit 45 are provided. The modulation unit 10 inputs the call voice signal from the handset 8 to the modulation circuit 10a, modulates the high frequency carrier wave f, which is the first carrier wave, and transmits it to the transmission line 3 through the bandpass filter 10b and the balancing circuit 14. The demodulation unit 11 is configured to send out
4, a demodulation circuit 11b for demodulating the modulated signal, and an audio signal amplification circuit 11c. The configuration is such that the call voice of the handset 1 is output from the handset 8 by outputting an audio signal.

On the other hand, the handset 1 includes a power separation unit 15 for separating the internal power of the handset 1 and the power of the monitor television camera 6 from the multiplexed signal sent from the base unit 4 via the transmission line 3, and a microphone 1.
6, a demodulator 18 that demodulates the modulated signal sent from the base unit 4 side and extracts a call audio signal, and an image from the monitor television camera 6. the signal to the video filter circuit 19
A video circuit that sends data to the base unit 4 through the
a calling signal generation circuit 19 that notifies the base unit 4 of a call by the operation of the above; and a balancing circuit 20 that is interposed between the circuit group and the transmission line 3 and balances unbalanced signals of the circuit group. , and a non-polarization circuit 44. The modulation section 17 is a microphone signal amplification circuit 1 that keeps the microphone signal constant and amplifies it up to a bell level.
The output signal from 7a is input to the modulation circuit 17b, and the high-frequency carrier wave f2, which becomes the second carrier wave (a high-frequency carrier wave that can be distinguished from the first carrier wave f on the base unit 4 side), is modulated, and the band The demodulation section 18 includes a bandpass filter 18 that limits the frequency band of the modulated signal from the balancing circuit 20.
a, and a demodulation circuit 18b for demodulating this modulated signal.
and an audio signal amplification circuit 18c, and the speaker 21 outputs the notification audio of the base unit 4 (11) by outputting a notification audio signal from the audio signal amplification circuit 18c.

The power source separation unit 15 also includes a power source separation circuit 15a that separates the power source from the multiplexed signal sent from the base unit 4 side, and a power source separation circuit 15a that detects a significant change in the power output value from the power source separation circuit 15a and detects a significant change in the power output value from the power source separation circuit 15a. It consists of a camera power switch 15b that controls on/off of power to the camera, and a shunt regulator 15c that keeps the supplied power current constant.

The base unit 4 and the slave unit 1 have connection terminals T,, T,' provided on the base unit 4 side, and connection terminals T2, ., T,' provided on the slave unit 1 side.
T and ' are connected by transmission lines 3 made of parallel electric wires, etc., respectively,
As mentioned above, in addition to the power supply, video signals, call audio signals, and calling signals necessary for information communication are multiplex transmitted between the base unit 4 and the slave unit 1 via the transmission line 3.

By the way, in the intercom system having the above-mentioned configuration, when the call button 2 of the handset 1 is operated, the call signal generation circuit 4
6 and outputs a calling signal.

This calling signal is sent to the base unit 4 side via the balancing circuit 20, the non-polarization circuit 44, and the transmission line 3, and is applied to the call detection unit 13 via the balancing circuit 14 of the base unit 4, and the calling signal is The speaker 5 of the base unit 4 is made to sound as follows.

On the side of the base unit 4 that has been called in this way, the superimposed voltage value on the power supply superimposition circuit 9 is changed to the slave unit 10 along with the sound of the speaker.
This constant current output is switched from the standby voltage value necessary for the calling operation of m to the operating dark voltage value necessary to supply power to the monitor television camera 6, and supplies constant current to the handset 1. In the handset 1, the power is separated and outputted by the power separation circuit 1.5a to activate the camera power switch 15b, and the power is supplied to the monitor television camera 6 through the shunt regulator 15c, thereby driving the monitor television camera 6.

When the monitor television camera 6 is driven, the video signal is transmitted from the video filter circuit 19 to the balancing circuit 20 and the transmission line 3 to the balancing circuit 14 on the parent FI 4 side, and then passes through the video signal receiving section 12 to the monitor. The image will be sent to the television 7 and displayed on the monitor television 7.

The call voice signal from the handset 8 is FM-modulated by the modulation circuit 10a having the first carrier wave f1, and this FM-modulated first carrier wave f is passed through the bandpass filter 1.
The signal is transmitted from 0b to the slave device 1 side via the balancing circuit 14 and the transmission line 3.

On the other hand, in the handset 1 receiving the signal of the carrier wave f, the modulated wave is inputted to the demodulation circuit 18b via the depolarization circuit 44, the balancing circuit 20, and the bandpass filter 18a of the demodulation section 18, and the modulated wave is inputted to the demodulation circuit 18b. The modulated wave of the carrier wave f is FM demodulated to obtain a speech audio signal output. Subsequently, this call audio signal is amplified by the audio signal amplification circuit 18c, and the call audio from the base unit 4 is output from the speaker 21 of the handset 1.

In addition, the call voice signal input from the microphone 16 on the handset 1 side is amplified by the microphone signal amplification circuit 17a, and is then amplified by the modulation circuit 17.
b, where the second carrier wave f2 is FM modulated,
It is sent from the bandpass filter 17c to the demodulation section 11 via the depolarization circuit 44, the balancing circuit 20, the transmission line 3, and further through the balancing circuit 14 on the base unit 4 side.
After being demodulated at step b, the voice signal is amplified by the voice signal amplification circuit 11c, and the handset 8 of the main unit 4 outputs the call voice.

In such a television intercom system, the first carrier wave f1 and the second carrier wave f2 are selected to have a frequency higher than the video signal frequency band of the monitor television camera 6 in order to prevent interference.

FIG. 5 is a diagram showing the relationship between the frequencies of these signals,
A direct current power supply voltage DC, a video signal V having a frequency band of several MHz, and a first carrier wave fl at a frequency above the video signal V.
The modulated wave a from the base unit 4 by the carrier wave f2 and the modulated wave from the slave unit 1 by the second carrier wave f2 are set to different frequencies, and these signals are multiplexed and transmitted through the transmission line 3. It is.

[Problem to be solved by the invention] By the way, the above-mentioned conventional system is ff1a! This is a one-to-one system between 4 and handset 1, but it is not possible to use a 2-wire TV intercom system that uses a configuration in which the standby voltage and operating voltage are switched in response to a call from the handset. ,
The relationship between the number of slave units and base unit is 1:N, N:1□ or NN
There is no system with a multi-station configuration such as N, and only systems using multi-pole transmission lines with complicated configurations were available.The present invention was made in view of the above-mentioned problems, and has a simple configuration. To provide a monitoring system for a two-wire television intercom system, which can be used for multi-station operation and can be monitored by operating a slave unit from a PA unit.

Further, the present invention as set forth in claim 3 provides a monitoring system for a two-wire television intercom system in which there is no need to supply standby voltage from the base unit, and therefore, supply setting is not necessary at the initial stage.

[Means for Solving the Problems] The present invention provides a slave device equipped with a monitor television camera, a parent device equipped with a monitor television, and a device that connects the parent device and the slave device to transmit video signals from the slave device and the parent device. It consists of a two-wire transmission line that transmits voice signals between the handset and handset, and during standby, a constant standby voltage is supplied to the handset via the transmission line, and ffHj! is activated by operating the calling means of the handset. When a call is made to the slave unit, the standby voltage value is instantaneously changed in conjunction with the operation of the calling means of the slave unit, and this change notifies the base unit of the call. This is a two-wire TV intercom system that supplies operating voltage to a machine via a transmission line for a certain period of time, and is equipped with a plurality of base units and one or more slave units, and is interposed between the base units and the slave units. A relay adapter is provided, and the relay adapter includes a base unit detection unit that is provided corresponding to each base unit to be connected and detects the operating voltage supplied from the base unit to the slave unit to detect the operation of the base unit. , a base unit selection unit that selects the activated base unit based on the detection output of the base unit detection unit and enables voltage supply from the base unit to the slave unit during operation; and an operation to be supplied from the base unit to the slave unit. a dummy load section that absorbs the operating voltage; and a switching section that controls the connection between the dummy load section and the main unit; If there is a detection output from all the base unit operation detection units corresponding to the connected base unit for a certain period of time, it is determined that the base unit is activated when a call is made by the slave unit, and the base unit corresponding to some of the connected base units If there is a detection output from the motion detection unit, it is determined to be a monitor signal, and the operating voltage from the base unit corresponding to the base unit motion detection unit that first generated the detection output is output to the slave unit, and the remaining parent unit The device is connected to a corresponding dummy load section via a switching section, and the invention according to claim 3 is the invention according to claim 1, in which the relay adapter and the main device are separated during standby, and the relay adapter is connected to the slave device. It supplies standby voltage to the terminal, and connects the relay adapter and the base unit when a call operation is made on the slave unit.

[Function] According to the present invention, at least a plurality of either a base unit or a slave unit is provided, a relay adapter is provided between the base unit and the slave unit, and the relay adapter allows calls from the slave unit to be received. In response, the call is relayed to the base unit and the supply voltage of the slave unit that performs the calling operation is set to the operating voltage, so the relay adapter connects the base unit and slave unit on a one-to-one basis. The basic 2-wire TV intercom system can be used as a multi-station system with multiple base units and multiple slave units, multiple base units and one slave unit, or one base unit and multiple slave units. can be constructed. When the monitor operating means provided on the base unit is operated, the operating voltage is supplied from the base unit whose monitor operating means was operated to the slave unit by the functions of the base unit operation detection unit and the base unit selection unit. This allows you to operate the handset and monitor the video from the handset. In this case, only the first base unit that is operated can be monitored, and even if the monitor operating means is operated on other base units, the operating voltage output from these base units is used as a dummy load. In the third aspect of the invention, the standby voltage is supplied to the slave device by a relay adapter.

[Example] The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.
・Transmission line 3...transmission line 3 via relay adapter 22
′... are connected to form a system.

FIG. 2 is a block diagram showing the relay adapter 22 in more detail, and shows the transmission lines 31 connected to the handsets 1...
・ is connected to the slave device selection unit 23 in the relay adapter 22 via the slave unit connection line 28 . . . , and each slave unit connection line 28 . Connected. On the other hand, the transmission line 3 connected to the base unit 4 is connected to the base unit selection unit 25 via the base unit connection line 29 within the relay adapter 22, and each base unit connection line 29... are connected to the parent machine operation detection section 26.... The slave unit selection unit 23 and the base unit selection unit 25 are connected by a two-wire connection line 27, and the connection line 27 includes a unidirectional buffer amplifier unit 30 whose input is on the slave unit selection unit 23 side.
A dummy load section 32 is connected in parallel to the output end of the buffer amplifier section 30, and a switching section 31 is connected to two parent device connection lines through which circuit.

To explain the operation of the circuit shown in FIG. 2 according to the diagram, during standby, the switching section 32 of the main device 4, which is controlled by the control signal S of the main device selection section 25, selects the dummy load section 31 The slave unit 1 is disconnected from the transmission line 3, the base unit connection line 29, the base unit selection unit 25, the connection line 27, the slave unit selection unit 23, the slave unit connection line 28..., the transmission line 3'... ...
One base unit 4 that is initially configured to connect directly to
A standby voltage is applied to each child unit 1 from .

When the call button 2 of the current handset 1 is operated, the standby voltage is forcibly dropped instantaneously by the handset 1, and this voltage drop causes the handset operation of the relay adapter 22 corresponding to the handset 1. It is detected by the detection unit 24.

In addition, the change in standby voltage is caused by the transmission M3', slave unit connection line 28,
After passing through the slave device selection section 23, the connection line 27 and the master device selection section 25
, the base unit connection line 29, the path of the transmission line 3, the connection line 27, the buffer amplifier section 3 for the modulated waves of the video signal and the call audio signal.
0..., dummy load section 32..., switching section 31
. . , are transmitted to the base unit 4 via the base unit connection line 29 and the transmission line 3 route, respectively. Here, when the handset operation detection section 24 detects a voltage drop during standby, the detection output is transmitted to the handset selection 23, and the transmission line 3° of the handset 1 whose call button 2 was operated is connected to the handset. ! The i28 and the connection line 27 in the relay adapter 22 are connected by the handset selector 23 with low loss.

In addition, all base units 4 activated by detecting the change in voltage during standby.
. . . The switching section 32 . The operating voltage is transmitted from the base unit 4 to the transmission line 3, the base unit connection line 29, the base unit selection section 25, the connection line 27, and the slave unit selection section 2.
3. The signal is transmitted to the handset 1 whose call button 2 is operated through the handset connection line 28 and the transmission line 3°, and the video signal and call audio signal of the handset 1 can be transmitted.

In addition, the transmission line 3 of the activated base unit 4 other than the above...
The switching unit 32 controlled by the base unit selection unit 25
Since the dummy load section 31... is connected through the parent unit connection line 29, it is in a state of being disconnected from the connection line 27, and the dummy load section 31... is used as a load to supply voltage during operation. continue.

As described above, the television intercom system of the present invention completes the start-up operation and shifts to the call operation. By the way, base unit 4... that has transitioned to call operation performs a timer operation, and the handset 8 of base unit 4... is forced to shut down in about 30 seconds when on-hook, and for about 3 minutes when off-hook (during a call). The call operation is now terminated. On the other hand, since the relay adapter 22 does not monitor the on-hook and off-hook states of the handsets 8 of the base units 4...
Whether or not is in a call state is determined by each base unit 4...! 13...
The main unit operation detection unit 26 determines whether the line voltage of the main unit connection line 29 connected to the main unit is the operating voltage value or the standby voltage value.
Judgment is made by comparing the detection at . Therefore, if the ff1li14 currently on the call is not the base unit 4 that is initially set to supply operating voltage at startup, but is another base unit 4, the initial setting of the parent unit 111.
It is possible to talk within 30 seconds, which is the operating period of No. 4, but if the time is longer than that, the initial setting of ff1fi4 will stop applying and supplying the operating voltage, making it impossible to talk. Therefore, at the moment when the initial setting main unit 4 finishes transmitting the operating voltage and returns to applying and supplying the standby voltage,
P! The mechanical motion detection unit 26... is connected to the parent a! which continues to supply voltage during operation. 14 (for example, base unit 4 during a call), outputs the detection output to base unit selection unit 25, and outputs the detection output to base unit selection unit 25.
The main unit 4 and the dummy load unit 31 continue to output voltage during operation by the switching unit 32 controlled by the main unit 4 and the dummy load unit 31.
・The two parent device connection lines of the parent device 4 and the connection line 27 are connected with low loss through the parent device selection section 25, and the voltage is continued to be applied and supplied to the child device 1... during operation. let At the same time, the base unit 4 and the dummy load unit 31 are initialized.
..., and connect the parent device connection line 29 and connection line 27 of the parent device 4 to the parent device 8! It is separated by the selection section 25.

As described above, by monitoring the line voltages of the base unit connection line 29 and the base unit selection unit 25 by the base unit operation detection unit 26..., the base unit 4 can be appropriately detected after the startup operation of the base unit 4. , the base unit 4 continues to supply voltage during operation to the slave unit 1, thereby enabling continuous communication between the master unit 14 and the slave unit 1. Now, the base unit 4 is equipped with a monitor operating means 40 for operating the slave 1!1 selected in advance by initial settings and monitoring the video from the slave 1.
When 0 is operated during standby, the operating voltage is output in the same way as when starting up.

On the other hand, all of the base unit operation detection units 26 corresponding to the base units 4 connected to the base unit selection unit 25 receive detection outputs within the first limited time after the standby state ( For example, if it occurs within 30 seconds of startup, it is determined that the activation is due to a call from the handset 1, and if some, but not all, of the base unit operation detection units 26 generate a detection output, the monitor It is equipped with @function that determines the action. In this case, the base unit motion detection unit 26 that generated the detection output determines that a monitor operation has been performed on the FF1 unit 4 corresponding to the base unit motion detection unit 26 that first generated the detection output, and the base unit 4 is connected to and supplied to a predetermined slave device 1 during operation. At this time, if the main device 4 is not the one that is separated from the dummy load section 32 to the switching section 31 so as to supply standby voltage in the initial setting, the main device selection section 25 controls the corresponding switching section 31 to The main unit 4 is separated from the dummy load section 32 and the main unit 4 is
Transmission line 3, parent device connection line 29, parent device selection section 25, connection line 27, child device selection section 23, child device connection line 2
8. Supply to the handset 1 via the transmission line 3'', and control the switching unit 31 corresponding to the other base unit 4 to switch to the other base unit 4.
is connected to the dummy load section 32. In this way, the predetermined handset 1 to which the operating voltage is supplied operates and transmits the video signal captured by the television camera 6 to the base unit 4 which is being operated as a monitor, and the video is monitored by the base unit 4. I can do it.

The block diagram of the relay adapter 22 shown in FIG.
Although the communication circuit from the base unit 4 to the base unit 4 is shown, the circuit from the base unit 4 to the slave unit 1, etc. is omitted as it is unnecessary for the explanation of the operation of the present invention. The configuration of the handset 1 is basically the same as the circuit shown in FIG. 4, but the configuration related to the call notification method is different, so the explanation is omitted. In addition, the outputs of A to C, x of the parent machine operation detection unit 26 in FIG. 2 are the parent tl! 1
This corresponds to inputs A-C and X of the selection section 25.

In each of the above embodiments, the dummy load section 32 is composed of a circuit having a resistance value corresponding to the power consumption capacity of the slave unit, but the resistance value may be made infinite, that is, open. , it is assumed that switching between this resistance value and infinity is performed as appropriate.

Also, the standby voltage and the operating voltage are set to the same voltage, and child 8!
Of course, the value of the current flowing through 11 or the time during which the current flows may be made different during standby and during operation.

Furthermore, the standby voltage may be applied from the relay adapter 22, and the relay adapter 22 may of course be incorporated into the slave tR1 or the base unit 2.

[Effects of the Invention] The present invention provides a slave unit equipped with a monitor TV camera, a base unit equipped with a monitor TV, a base unit and a slave unit, and a video signal from the slave unit, a base unit and the slave unit, and a video signal from the slave unit. It consists of a two-wire transmission line that transmits call voice signals between the terminals, and during standby, a constant standby voltage is supplied to the slave unit via the transmission line, and when the base unit is called by operating the calling means of the slave unit. The standby voltage value is instantaneously changed in conjunction with the operation of the calling means of the slave unit, and this change notifies the base unit of the call, and when the base unit starts up in response to a call from the slave unit, the slave unit operates. A two-wire TV intercom system that supplies voltage for a certain period of time via a transmission line, which includes multiple base units and one or more slave units, and a relay adapter interposed between these base units and slave units. The relay adapter is provided with a base unit detection unit that is provided corresponding to each of the m units connected and detects the operating voltage supplied from the base unit to the slave unit to detect the operation of the base unit, and the base unit. A base unit selection unit that selects the activated base unit based on the detection output of the detection unit and enables voltage supply from the base unit to the slave unit during operation, and absorbs the voltage during operation that should be supplied from the base unit to the slave units. a dummy load section for controlling the connection between the dummy load section and the main device, and a switching section for controlling the connection between the dummy load section and the main device, and the main device is equipped with a monitor operating means for arbitrarily outputting the operating voltage from the main device, If there is a detection output for a certain period of time from all base unit operation detection units corresponding to the machine, it is determined that the base unit is activated when a call is made by the slave unit, and the base unit operation detection units corresponding to some of the connected base units If there is a detection output of It is connected to the dummy load section via a switching section, and the basic 2-wire TV intercom system, which connects the base unit and slave unit on a one-to-one basis using a relay adapter, can be used to connect multiple base units and multiple slave units. When a multi-station system can be constructed such as a slave unit, multiple base units and one slave unit, or one base unit and multiple slave units, and the monitor operation means provided on the base unit is operated. By the functions of the parent device operation detection section and the parent device selection section, the operating voltage is supplied from the parent device operated by the monitor operating means to the child device to operate the child device and display the image from the child device. In particular, the number of base units that can be monitored is only the first base unit that is operated, and even if the monitor operating means is operated on another base unit, these PAt
The operating voltage output from Ill can be absorbed by the dummy load section, which has the effect of not interfering with the operation.

Furthermore, the invention as set forth in claim 3 has the effect that there is no need to supply standby voltage from the master unit, and no initial setting is required for this purpose.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention, Fig. 2 is a detailed block diagram of the same as above, Fig. 3 is a schematic configuration diagram that is the basis of the present invention, and the main cause is the same block as above. FIG. 5 is an explanatory diagram of the frequency arrangement of signals transmitted through the same transmission line. 1 is the slave unit, 2 is the push button, 3, 3' is the transmission line, 4 is the base unit, 2
2 is a relay adapter, 23 is a slave unit selection unit, 24 is a slave unit operation detection unit, 25 is a base unit selection unit, 26 is a base unit operation detection unit, 2
7 is a connection line, 28 is a slave unit connection line, 29 is a master unit connection line, 3
0 is a buffer amplifier section, 31 is a switching section, 32 is a dummy load section, and 40 is a monitor operating means. Agent Patent Attorney Ishi 1) Chief Figure 7

Claims (3)

[Claims] (1) Connect a slave unit equipped with a TV monitor camera, a base unit equipped with a TV monitor, and the base unit and slave unit to receive video signals from the slave unit and voice signals from calls between the base unit and the slave unit. During standby, a constant standby voltage is supplied to the handset via the transmission line, and when a call is made to the base unit by operating the calling means of the handset, the above standby voltage value is supplied to the slave unit through the transmission line. The voltage changes instantaneously in conjunction with the operation of the calling means of the slave unit, and this change notifies the base unit of the call, and also transmits the operating voltage from the base unit to the slave unit when activated in response to a call from the slave unit. This is a two-wire TV intercom system that supplies power for a certain period of time through a TV intercom system, which includes a plurality of base units and one or more slave units, and a relay adapter that is interposed between these base units and slave units. includes a base unit detection section that is provided corresponding to each base unit connected to the base unit and detects the operating voltage supplied from the base unit to the slave unit to detect the operation of the base unit, and a detection unit for the base unit detection unit. A base unit selection section that selects the activated base unit based on the output and enables voltage supply during operation from the base unit to the slave unit; and a dummy load unit that absorbs the voltage during operation that should be supplied from the base unit to the slave unit. and a switching unit for controlling the connection between the dummy load unit and the base unit, and the base unit includes a monitor operating means for arbitrarily outputting an operating voltage from the base unit, and the base unit is equipped with a monitor operating means for arbitrarily outputting a voltage during operation from the base unit, and the base unit is equipped with a monitor operating means that outputs a voltage during operation from the base unit, and the base unit is equipped with a monitor operating means that outputs a voltage during operation from the base unit, and the switch unit controls the connection between the dummy load unit and the base unit. If the detection output from all the base unit operation detection parts is within a certain period of time, it is determined that the base unit is activated when a call is made by the slave unit,
If there is a detection output from a base unit motion detection unit that corresponds to a part of the connected base unit, it is determined to be a monitor signal, and the operation from the base unit that corresponds to the base unit motion detection unit that first generated the detection output is determined as a monitor signal. A monitoring system for a two-wire television intercom system, characterized in that the current voltage is output to a slave unit, and the remaining base unit is connected to a corresponding dummy load unit via a switching unit. (2) The two-wire television set according to claim 1, characterized in that the standby voltage and the operating voltage are equal in value, but the current value or the time during which the current continues to flow is different between the standby state and the operating state. Intercom system monitoring method. (3) During standby, the relay adapter and base unit are disconnected, and standby voltage is supplied from the relay adapter to the slave unit, and when there is a call operation on the slave unit, the relay adapter and base unit are connected. 2. A monitor system for a two-wire television intercom system according to claim 1.