JPH10136106A - Video doorphone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video doorphone system with an inexpensive control circuit by controlling a doorphone slave set with a camera with an interphone master set with a television receiver of a simple circuit configuration. SOLUTION: This system is provided with a doorphone slave set with a camera and an interphone master set 2 with a television receiver that displays a video image picked up by the doorphone slave set with camera, and the interphone master set 2 with a television receiver and the doorphone slave set with a camera are connected by a 2-wire balanced cable and the interphone master set 2 with a television receiver supplies power to the doorphone slave set with a camera and controls the operation. In this case, the interphone master set 2 with a television receiver is provided with a power supply operation means 241 to change a power supply voltage for the control of a plurality of operating states of the doorphone slave set with a camera, and the doorphone slave set with a camera is provided with a power supply operation identification means to detect and identify the voltage of the power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television intercom system in which an intercom master unit with a television and an intercom slave unit with a camera are connected by two wires.

[0002]

2. Description of the Related Art An image taken by a television camera of a doorphone slave unit with a camera (hereinafter, referred to as a camera slave unit) is displayed on a monitor television of an intercom master unit with a television (hereinafter, referred to as a TV master unit), so that a visitor can enjoy it. In order to simplify the connection between the TV base unit and the camera slave unit, a TV door phone system for confirming the image and making a call is proposed, which is connected by a two-wire balanced cable as shown in FIGS. Have been. In this television doorphone system, the television master unit shown in FIG. 8 supplies power to the camera slave unit shown in FIG. 9 and also supplies a control signal in multiplex transmission in which an audio signal and a video signal are superimposed on the power supply DC voltage. It is multiplexed to control the call operation between the TV master unit and the camera slave unit.

The control of the above-mentioned call operation is performed by the microcomputer 241.
The power supply circuit 232 is controlled by the control. Specifically, as shown in FIG. 10A, in a normal standby state, the video circuit and the audio circuit of the camera slave unit are inoperative, and the voltage is set to a voltage low enough to detect only the call switch. For example, when a standby voltage of approximately 6 V is used, in a call state during operation, a communication operation voltage of approximately 14 V, for example, is output to the line terminal 25 to operate the video circuit and the audio circuit, and is applied between the two lines. The power is supplied from the television master set to the camera slave set.
The control of the operation mode of the camera slave unit, such as the monitor mode operation in which only the video is checked and the telephone call is not made in the TV master unit, is performed by controlling the audio FM modulation circuit 225 by the control of the microcomputer 241 from the TV master unit. Will be More specifically, for example, a control signal is generated by an FM carrier signal of approximately 6.5 MHz, and the control signal is demodulated on the camera slave unit side. That is, as shown in FIG. 10B, in the monitor mode in which only the image is confirmed in the TV master unit and no telephone call is made when the above-mentioned call operation voltage is applied, the control signal based on the FM carrier signal is not generated. As shown in FIG. 10 (c), in the video call mode for performing the video check and the call, the control signal based on the FM carrier signal is generated,
Each control is performed. The camera slave unit shown in FIG. 9 uses the carrier detection control circuit 1
5, the speaker amplifier operation switch circuit 1
35 is turned off. Then, for example, control of a monitor mode operation in which only a video is confirmed and a telephone call is not performed in the television master device is performed.

[0004]

By the way, the FM carrier signal used for controlling the above-mentioned camera slave unit is a signal of a specific frequency band which does not affect the audio signal and the video signal. It is multiplexed using a frequency multiplexing circuit and transmitted. Therefore, a complicated circuit is required for each of the television master unit and the camera slave unit. Further, operations other than the above-mentioned monitor mode, for example, operating only the speaker amplifier for the call speaker without operating the TV camera of the camera slave,
A more complicated circuit is required to perform an operation such as a back tone mode for allowing a visitor to confirm that the operation of the call switch has been performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to control an intercom slave unit with a camera by a simple circuit configuration by a master unit with a television intercom. It is an object of the present invention to provide a TV intercom system for a control circuit.

[0006]

According to a first aspect of the present invention, there is provided a television intercom system, comprising: a door intercom unit with a camera for outputting a video signal photographed by a television camera; An intercom master unit with a television for displaying images taken by the intercom slave unit with a camera, and the intercom master unit with a television and the intercom slave unit with a camera are connected by a two-wire balanced cable. In a television doorphone system for supplying power to a camera doorphone slave unit and performing operation control, the television intercom master unit sends the camera doorphone slave unit to a camera doorphone slave unit for controlling a plurality of operation states of the camera doorphone slave unit. Power supply operating means for changing the magnitude of the voltage or current of the power supply In addition, the intercom slave unit with a camera has a power operation identification unit that detects and identifies a change in the magnitude of the voltage or current of the power input, and the intercom slave unit with the camera performs a plurality of operations from the standby state by the intercom master unit with the television. The state is controlled. As a result, the intercom slave unit with camera is controlled to a plurality of operating states by a change in the voltage or current of the power supply.

According to a second aspect of the present invention, there is provided a television intercom system, comprising the steps of:
The rising form of the power supply change in a short time is used. As a result, the camera-equipped intercom slave unit is controlled by a short-time change in the voltage or current of the power supply, and the operation state changes.

According to a third aspect of the present invention, there is provided a television intercom system according to the first or second aspect, wherein the switch for stopping the operation of the speaker for outputting the received voice based on the output from the power operation identifying means. Means. As a result, the operation of the speaker that outputs the received voice is stopped and controlled.

In a television intercom system according to a fourth aspect, the switch means according to the third aspect operates the speaker by an on operation of a call switch for calling the intercom master unit with a television. As a result, the speaker is controlled to operate by turning on the call switch.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a television door phone system according to an embodiment of the present invention; FIG.

[First Embodiment] FIG. 1 is a block diagram of a TV base unit of a TV door phone system according to a first embodiment.
FIG. 2 is a block diagram of the camera slave unit. FIG.
FIG. 3 is a circuit configuration diagram of a power receiving unit that is a main part thereof. FIG. 4 is a waveform diagram of an input voltage of the camera slave unit shown in FIG.

This television intercom system has a camera sub unit 1 for outputting a video signal photographed by a television camera, and a video signal inputted and photographed by the camera sub unit in the same manner as described in the conventional example. And a television main unit 2 that projects The TV base unit 2 and the camera slave unit 1 are connected by a two-wire balanced cable. The present invention is not limited to this single system configuration. For example, the present invention has a function equivalent to that of the TV base unit 2 and is installed in a place other than the room where the TV base unit is installed. A TV intercom system or the like including an intercom secondary master unit with a television for displaying an image shot by the device 1 may be used.

The camera slave unit 1 is installed, for example, at an entrance or the like, and includes a video unit 11, an audio unit 12 for making a telephone call with a TV master unit 2 described later, and a power supply for an internal circuit of the camera slave unit 1. And a power receiving unit 13 for each of them, all of which are connected to the terminal 14.

The video section 11 is for photographing a visitor and outputting a video signal. The television camera 111 outputs the captured video signal. The video signal from the television camera 111 is FM-modulated into, for example, an FM signal of a predetermined frequency. And a video modulation circuit 112.

The voice section 12 includes a speaker 121 for outputting a received voice and the like, a microphone 122 for inputting a transmitted voice and converting it to an electric voice signal, and a speaker amplifier 123 for amplifying the voice signal and driving the speaker 121. , Microphone 122
Amplifier 124 for amplifying the audio signal from
And an audio 2-wire 4-wire conversion circuit 125 that converts 4-wire wiring into 2-wire wiring in order to transmit voice signals for transmission and reception through a pair of wirings.

The power receiving unit 13 is a circuit for obtaining a DC power supply from the TV base unit 2 described later without affecting the audio signal and the video signal, and converts the input impedance viewed from the terminal 14 into a predetermined value. Conversion circuit 131, a first voltage detection switch circuit 132,
A first stabilized power supply 133 for supplying power to circuits other than the speaker amplifier 123, and a power supply operation identification unit that detects and identifies a change in the magnitude of the power supply input voltage applied to the terminal 14 Two-voltage detection / control circuit 134
A speaker amplifier operation switch circuit 135 corresponding to a switch for stopping only the operation of the speaker 121 by an output from the second voltage detection / control circuit 134;
It has a voltage detection / self-holding circuit 136 and a second stabilized power supply 137 for a speaker amplifier. See Figure 3 for details.
, A Zener diode ZD1 corresponding to the second voltage detection / control circuit 134, and a transistor switch Q1 corresponding to the speaker amplifier operation switch circuit 135.
A Zener diode ZD2 corresponding to the first voltage detection / self-holding circuit 136, a transistor switch Q2,
And a call switch SW that is connected in parallel to the transistor switch Q2 to call the television master set 2 and operate the speaker 121 by closing the circuit.

The TV base unit 2 is installed, for example, in a living room of a house such as a kitchen, and includes a video unit 21, an audio unit 22 for making a call with the camera slave unit 1, a power supply unit 23, and a TV base unit. The control unit 24 forms a power supply operation unit for changing the magnitude of the voltage or current of the power supply of the power supply unit 23 to the camera slave unit 1 in order to control the internal control of the camera slave unit 1 and a plurality of operation states of the camera slave unit 1 , Which are all connected to the terminal 25.

The video section 21 is for inputting a video signal and displaying an image, and is provided with a television circuit section 211 having a television monitor for displaying an image captured by the camera sub-unit 1 and an input from the camera sub-unit 1. A video amplification circuit 212 for amplifying and demodulating the FM-modulated video signal to a predetermined signal level.

The voice unit 22 has a handset 221 having a speaker for outputting a reception voice and the like and a microphone for inputting a transmission voice and converting it into an electric voice signal, and drives a speaker of the handset 221 by amplifying the voice signal. Amplifier 222, a microphone amplifier 223 for amplifying an audio signal from the microphone of the handset 221, and a two-wire wiring for transmitting and receiving voice signals transmitted and input through a pair of wirings by four-wire wiring. And an audio 4-wire 2-wire conversion circuit 224 for converting the audio into a voice.

The power supply section 23 has a power supply circuit 231 for generating power for an internal circuit of the TV base unit 1 and a power supply circuit 232 for generating power for the camera slave unit 1.

The control unit 24 controls the operation of each circuit of the camera slave unit 1 and the television master unit 2, and controls a plurality of operating states of the camera slave unit 1 so as to control the power supply to the camera slave unit 1. By power supply operation means that changes the magnitude of the voltage,
The output voltage of the power supply circuit 232 is adjusted. The control unit 24 includes, for example, a one-chip microcomputer 241
And a program that defines a predetermined operation procedure by the control unit in a storage unit therein, and a control unit 2
4 to store data that can be processed. The microcomputer 241 receives an output from a call detection circuit 242 for detecting that the call switch SW of the camera slave 1 has been operated and called by a change in the power supply voltage of the two-wire balanced cable.

In the above circuit configuration, the TV base unit 2
Changes the magnitude of the voltage of the power supply to the camera slave unit 2 by the control unit 24 corresponding to the power operation means, and controls a plurality of operating states of the camera slave unit 1. That is, the power supply circuit 232 is switched by the microcomputer 241 to a plurality of output voltages toward the line terminal 25 even when the camera slave device 1 is in the operating state, as shown in FIG. The line terminal 25 and the terminal 1 are connected between the TV base unit 2 and the camera slave unit 1.
4 are connected to each other by a two-wire balanced cable. The direct current supplied from the television base unit 2 to the camera slave unit 1 is multiplexed with the audio signal and the video signal. Using the change in the first voltage V1 which is the call operation voltage from the standby voltage Vw or the first voltage V1 which is the call operation voltage from the standby voltage Vw through the second voltage V2, each of the camera slave units 1 is used. Controlling the operation mode. The time of the rising change in these two steps is set to about several 100 ms.

On the other hand, when the voltage applied to the terminal 14 changes from the standby voltage Vw to the second detection voltage V2 or higher, the Zener diode ZD1 is connected to the transistor Q2 from the Zener diode ZD1. It is set to a Zener voltage V2 capable of driving a current. Therefore, when the power supply voltage applied to the terminal 14 of the camera slave 1 is equal to or higher than the second detection voltage V2, the transistor Q2
Is turned on, the transistor switch Q corresponding to the operation switch circuit 135 of the speaker amplifier 123 is turned on.
1 is turned on.

After the transistor switch Q1 is turned on, the Zener diode ZD2 can maintain the ON state of the transistor Q2 when the voltage applied to the terminal 14 is equal to or higher than the first voltage V1. It is set to a slightly lower Zener voltage V1-. Then, once the transistor switch Q1 is turned on, the base current is also supplied to the transistor Q2 from the Zener diode ZD2, and the voltage at the point A is maintained at about 1 V or more, as shown in FIG. 4B. In the case of the rising voltage of the operation mode 2, even if the power supply voltage decreases to the first voltage value V1 after the transistor switch Q1 is turned on, the input voltage (point B voltage) to the second stabilized power supply 137 is not changed. The speaker amplifier 123 is kept in the operating state while being maintained at the operable voltage. When the voltage applied to the terminal 14 at the time of rising is higher than the first detection voltage V1, the first voltage detection switch circuit 132 and the first stabilized power supply 13
3 also works. Accordingly, other circuits except the speaker amplifier such as the microphone amplifier 124 of the video unit 11 and the audio unit 12 operate normally, and the camera slave unit 1 shifts from the standby state to the operation mode 2, that is, the “visitor call mode”.

In the "visitor call mode", the call with the visitor is terminated, and the voltage applied to the terminal 14, which is the voltage of the power supply to the camera slave 1 output from the television master 2, is
When the voltage drops below the first detection voltage V1 and changes to the standby voltage Vw, no current flows from the Zener diode ZD2 through the base of the transistor Q2, and the transistor Q2
Is turned off. Then, the camera slave unit 1 returns to the standby state from the operation mode 2, that is, the “visitor call mode”.

In the above circuit configuration, when the voltage applied to the terminal 14, which is the power supply voltage applied to the camera slave 1, is higher than the first detection voltage V1 and lower than the second detection voltage V2. The base current does not flow from the Zener diode ZD1 to the transistor Q2. Therefore, the transistor Q2 continues to be in the off state, so that the transistor switch Q1 continues to be in the off state. As a result, the second stabilized power supply 137 for the speaker amplifier 123
, The power supply voltage is not supplied to the speaker amplifier 123, and the speaker amplifier 123 does not operate. On the other hand, in the first voltage detection switch circuit 132, the Zener diode ZD3 is turned on to be turned on, the first stabilized power supply 133 is operated, and the other circuits except the speaker amplifier are operated. Therefore, the operation mode 1 shown in FIG.
, The other circuits such as the video section 11 and the microphone amplifier 124 operate normally without operating the speaker amplifier 123 of the camera slave unit 1, and the camera slave unit 1 shifts from the standby state to the operation mode 1. That is, the mode shifts to the “monitor mode”, which is an outdoor monitoring mode using video.

In addition, when the call button is operated and the call switch SW is turned on when the camera slave unit 1 is in a standby state, the call switch SW for calling the TV master unit 2 is turned on by the camera master unit 1. When it is detected that the handset 2 is in a calling state, the power supply voltage applied to the terminal 14 of the camera handset 1 is set to the first detection voltage V1 or higher in order to immediately shift the camera handset 2 to the “visitor call mode”. Start up to power supply voltage. The response time of the operation voltage rise from the TV base unit 2 is set to a time shorter than the call button operation time of the visitor (it is confirmed that the actual time is at least 150 ms or more by the inventors). The voltage applied to the terminal 14 immediately rises. When the voltage applied to the emitter of the transistor switch Q1 of the second stabilized power supply 137 for the speaker amplifier 123 rises according to the above, the switch SW is closed. Therefore, the transistor switch Q1 is connected to the Zener diode ZD1 for detecting the second detection voltage V2 and the transistor Q2.
It is immediately turned on without being driven by this circuit. That is, under the condition that the call switch SW is in the ON state, the delay is caused by the circuit for detecting the second detection voltage V2 constituted by the Zener diode ZD1 for detecting the second detection voltage V2 and the transistor Q2. As described above, the speaker amplifier becomes operable, and as described above, the speaker amplifier becomes operable by the power supply operation identification of the rising form of the power supply change in a short time, and the prompt response of the ringing chime sound can be secured. , It is possible to immediately shift from the standby state to the operation state.

[Second Embodiment] In the configuration of the second embodiment shown in FIGS. 5 to 7, the camera slave unit 1 also operates the power supply by detecting and identifying a change in the voltage or current of the power supply input. It is possible to control from the standby state to a plurality of operation states by the identification means. FIG. 5 is a block diagram of a camera slave according to the second embodiment. FIG. 6 is a circuit configuration diagram of a power receiving unit, which is a main part of the power receiving unit. FIG. 7 is a waveform diagram of the input voltage of the camera slave unit shown in FIG.

This television intercom system supplies the television main unit 2 with a power supply voltage from the standby voltage Vw to the first voltage V1 or from the standby voltage Vw to the second voltage V2 and the first voltage V1.
The only difference from the first embodiment is the mode of change to and the configuration of a part of the camera slave 1, and the other components are the same as those of the first embodiment.

The power receiving unit 13 of the camera slave unit 1 is
The same as the impedance conversion circuit 131 and the first voltage detection switch circuit 132 of the first embodiment, the operation voltage V2
Control the voltage supply to the first stabilized power supply 133 by the second
Voltage detection switch circuit 132 and speaker amplifier 123
A first stabilized power supply 133 for supplying power to other circuits except for the first circuit, and a second power supply operation identification means for detecting and identifying a change in the magnitude of the power supply input voltage applied to the terminal 14.
A voltage detection circuit 134, a speaker amplifier operation switch circuit 135, a control signal holding circuit 136, a second stabilized power supply 137 for the speaker amplifier, and a first voltage detection delay trigger generation circuit 138 corresponding to a power supply operation identification unit. have. Specifically, as shown in FIG. 6, the second voltage detection circuit 134 includes a Zener diode ZD1, and the first voltage detection / trigger generation circuit 138 includes a Zener diode ZD.
2, and outputs a detection result of a change in the magnitude of the power supply input voltage to a D flip-flop circuit corresponding to the control signal holding circuit 136. The control signal holding circuit 1
In the D flip-flop circuit 36,
And a call switch SW for operating the speaker 121 by a closing operation is connected to the Set terminal.

In the circuit configuration described above, the change in the power supply voltage of the TV base unit 2 is, as shown in FIG. 7, the standby voltage in the operation mode 1, that is, the "monitor mode" which is the outdoor monitoring mode using images. After a short time t1 after the voltage once rises from Vw to the first voltage V1, a two-stage change is made to further increase to the second voltage V2. The above-mentioned t1 is approximately 100 ms in this case. Further, in the operation mode 2, that is, in the "visitor call mode", the power supply voltage changes in one step from the standby voltage Vw to the second voltage V2 which is the operation voltage.

When the voltage applied to the terminal 14 is the standby voltage Vw, the camera slave unit 1 uses the transistor Q of the first voltage detection / trigger generation circuit 138 and the second voltage detection circuit 134.
1 and Q2 are both off, and the D input and T input of the D flip-flop are both at L level. Further, since the D flip-flop Reset input is at the H level and the Set input is at the L level, the control signal output Q is in the reset state, that is, at the L level, and the standby state is maintained.

In the case of the rise of the "monitor mode" of the operation mode 1 shown in FIG. 7A, when the voltage applied to the terminal 14 rises from the standby voltage Vw to the first voltage V1, the first voltage is detected. The output of the transistor Q1 of the trigger generation circuit 138, that is, the reset of the D flip-flop
The t input switches from the H level to the L level, and the D flip-flop enters an active state. Further, the delay output by R and C of the first voltage detection / trigger generation circuit 138 is switched from L level to H level after a delay of t2 time, and a trigger for holding the D input level of the D flip-flop is input to the T input. give. At this time, since the voltage applied to the terminal 14 is still at the first voltage V1, the output of the second voltage detection circuit 134, that is, the D input of the flip-flop remains at the L level, and the Q of the flip-flop as the control signal output is output. The output is held at the L level. Therefore, when the power supply voltage applied to the terminal 14 of the camera slave unit 1 changes as described above, the speaker amplifier operation switch circuit 135 is maintained in the off state, and the operation mode 1 is switched to the operation mode 1 as in the first embodiment. It is possible to obtain.

The operation mode 2 shown in FIG.
Terminal 1 in the case of "Visitor call mode"
4 rises from the standby voltage Vw to the second voltage V2, the output of the transistor Q1 of the first voltage detection / trigger generation circuit 138, that is, the Reset input of the D flip-flop switches from H level to L level, The D flip-flop becomes active. Further, the delay output by R and C of the first voltage detection / trigger generation circuit 138 is switched from L level to H level after a delay of t2 time, and a trigger for holding the D input level of the D flip-flop is input to the T input. give. At this time
The output of the voltage detection circuit 134, that is, the D input of the flip-flop is switched from the L level to the H level at the same time as the output of the transistor Q1 of the first voltage detection / trigger generation circuit 138. Then, the Q output of the D flip-flop as the control signal output switches from the L level to the H level, and this H level is held. Therefore, when the power supply voltage applied to the terminal 14 of the camera slave 1 changes as described above, the speaker amplifier operation switch circuit 1
35 is turned on, and the state of the operation mode 2 can be obtained as in the first embodiment.

When the call button is operated and the call switch SW is turned on when the camera slave unit 1 is in the standby state, the call switch SW for calling the TV master unit 2 is turned on. When it is detected that the handset 2 is in the calling state, the power supply voltage applied to the terminal 14 of the camera handset 1 is set to the second detection voltage V2 or more in order to immediately shift the camera handset 2 to the “visitor call mode”. Start up to power supply voltage. As a result, the D flip-flop Set
The input changes from the L level to the H level, and the Q output of the D flip-flop is unconditionally set to the H level and held. Therefore, under this condition, there is no delay element due to the first voltage detection / trigger generation circuit 138, and the transition from the standby state to the operation state of the operation mode 2 is made.

As described above, the speaker amplifier can be operated by the power supply operation discrimination in the rising form of the power supply change in a short time, the prompt response of the ringing chime sound can be ensured, and the standby state can be immediately changed. It is possible to shift to the operating state.

The first voltage duration t shown in FIG.
The relationship between 1 and the delay time t2 for generating a delay trigger is set so that t1> t2.

According to the television doorphone system described above, the camera-equipped doorphone slave unit 1 is controlled to a plurality of operating states by a change in the magnitude of the voltage or current of the power supply, so that it is controlled by a simple circuit configuration. Thus, it can be controlled by an inexpensive control circuit. Also,
Since the intercom unit with camera 1 is controlled by a change in the magnitude of the voltage or current of the power supply for a short time and the operation state changes, there is no sense of incongruity due to the control. In addition, since the operation of the speaker that outputs the received voice is controlled to be stopped, the speaker operation can be switched between the “monitor mode” and the “visitor call mode” with a simple configuration. Can be controlled by
Further, since the speaker is controlled to operate by turning on the call switch, it is possible to shift from the “monitor mode” to a normal “visitor call mode” by turning on the call switch by a simple configuration. And can be controlled by an inexpensive control circuit.

In the embodiment described above,
Although the power supply operation identification means of the camera slave uses a Zener diode as an example, it has been described by way of example of the one that identifies a short-term voltage change. However, the present invention is not limited to this only, and for example, A to detect the terminal voltage of the machine
It may be constituted by a microcomputer or the like having a D converter and identified by processing based on a software program. In this case, there is an effect that more operation modes can be controlled by discriminating a voltage change in a short time.

[0040]

According to the television intercom system of the first aspect, the intercom slave unit with camera is controlled to a plurality of operating states by a change in the voltage or current of the power supply, so that a simple circuit configuration is provided. Can be controlled by
Thus, it can be controlled by an inexpensive control circuit.

In a television intercom system according to a second aspect, in addition to the effects of the first aspect, the intercom slave unit with a camera is controlled by a change in the voltage or current of the power supply in a short time. Therefore, it is possible to immediately shift from the standby state to the operation state.

Further, in the television door phone system according to the third aspect, in addition to the effects of the first or second aspect, the operation of the speaker for outputting the received voice is controlled to be stopped. For example, the speaker operation such as the “monitor mode” and the “visitor call mode” can be switched, and thus, can be controlled by an inexpensive control circuit.

Further, in the television door phone system according to the fourth aspect, in addition to the effect of the third aspect, the speaker is controlled to operate by turning on the call switch. For example, the mode can be switched from the "monitor mode" to the normal "visitor call mode" by turning on the call switch, and thus can be controlled by an inexpensive control circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram of a TV base unit of a TV door phone system according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a camera slave unit of the television door phone system shown in FIG.

FIG. 3 is a circuit configuration diagram of a power receiving unit which is a main part of the camera slave unit shown in FIG. 2;

FIG. 4 is a waveform chart of an input voltage of the camera slave unit shown in FIG. 2;

FIG. 5 is a block diagram of a camera slave unit of the TV door phone system according to the second embodiment.

FIG. 6 is a circuit configuration diagram of a power receiving unit which is a main part of the camera slave unit shown in FIG.

FIG. 7 is a waveform diagram of an input voltage of the camera slave unit shown in FIG. 5;

FIG. 8 is a block diagram of a conventional television base unit.

FIG. 9 is a block diagram of a conventional camera slave unit.

10A and 10B are explanatory diagrams of control in a conventional example, wherein FIG. 10A is a waveform of a terminal voltage, FIG. 10B is a diagram of a carrier signal spectrum in a monitor mode, and FIG. 10C is a diagram of a carrier signal spectrum in a visitor talk mode. Is

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Door phone handset with camera (camera handset) 134 2nd voltage detection / control circuit (power supply operation identification means) 135 Speaker amplifier operation switch (switch means) SW call switch 2 Intercom master unit with TV (TV master unit) 241 microcomputer (Power supply operation means)

Claims (4)

[Claims] 1. An intercom slave unit with a camera for outputting a video signal photographed by a television camera, and an intercom master unit with a television for inputting a video signal and displaying an image photographed by the intercom slave unit with a camera. , 2 between the intercom master unit with TV and the intercom slave unit with camera.
In a TV intercom system connected by a line balanced cable and the TV intercom master unit supplies power to the camera intercom slave unit and controls the operation, the TV intercom master unit performs a plurality of operations of the camera intercom slave unit. A power supply operating means for changing the magnitude of the voltage or current of the power supply to the camera-equipped doorphone handset for controlling the state, and the camera-equipped doorphone handset is provided with a power input voltage or current magnitude change. A television intercom system, comprising: a power intercom identification unit for detecting and identifying an intercom with a camera, wherein the intercom with a camera is controlled from a standby state to a plurality of operating states by an intercom master with a television. 2. The video door phone system according to claim 1, wherein the power supply operation is performed in a form of a short-time power supply change from a standby state. 3. The television according to claim 1, wherein the intercom with camera has switch means for stopping an operation of a speaker for outputting a received voice according to an output from the power operation identification means. Door phone system. 4. The television doorphone system according to claim 3, wherein said switch means operates said speaker by turning on a call switch for calling said intercom master unit with television.