JPH1051763A - Video intercom system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video doorphone system to which a plurality of camera sets can be connected at a low cost. SOLUTION: This system is provided with an intercom slave set 1 with a camera, a camera set 3 providing an output of a video signal, and an intercom master set 2 with a television receiver displaying a video image receiving the video signal and picked up by the intercom slave set 1 and the camera set 3, and the intercom master set 2 with a television receiver and the intercom slave set 1 with a camera are connected by a 2-wire balanced cable. In this case, the camera set 3 has a larger output impedance than the characteristic impedance of the 2-wire balanced cable and at least two of the camera sets 3 are connected from each connection terminal of the intercom master set 2 with a televisions receiver and a terminator 5 is connected, which has nearly equal impedance to the characteristic impedance of the 2-wire balanced cable is connected to the end of connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video door phone system for transmitting a video signal and making a telephone call.

[0002]

2. Description of the Related Art Conventionally, for example, in a house with a store, a TV door phone system for remotely monitoring the inside of a store or confirming an image of a visitor to make a call is shown in FIG.
As shown in the system configuration diagram of FIG. 1, a door phone slave unit 1 with a camera installed at an entrance or the like, a monitor TV 6 and an intercom device 7 installed in a living room or the like in a house, and a monitoring camera installed in a store. It has a certain camera device 3 and is connected to each other by a connection cable L which is a two-wire balanced cable. When monitoring a plurality of places in the store or other places in the house other than the place where the master unit 2 is installed, the camera device 3 similarly connected by a two-wire balanced cable is appropriately disposed.

In the above configuration, the monitor television 6
In normal operation, an image from the camera device 3 is displayed at predetermined time intervals by an operation program of a built-in CPU serving as a control circuit, or the camera slave unit 1 or the camera device 3 is operated by a resident operating a predetermined operation switch. The video signals are switched and each video is projected. When the visitor operates the intercom call switch of the camera slave, the video signal is switched to that from the camera slave 1. The resident confirms the image of the visitor and makes a call using the intercom device 6.

On the other hand, in a TV door phone system of an intercom master unit 2 with a TV, in which two intercom units 1 with a camera can be installed, as shown in FIG. 10B, the intercom unit 1 with a camera is connected under normal use conditions. There is also proposed a TV door phone system in which one camera device 3 is connected to a terminal to check a video of a visitor to make a call and monitor the inside of the store. In this TV intercom system, at a location other than the location where the intercom base unit 2 with the television is installed, the intercom with the television is capable of remotely monitoring the inside of the store or confirming the image of the visitor and making a telephone call. A device in which a secondary master unit is installed has also been proposed.

[0005]

In the former TV door phone system, the monitor TV 6 has a predetermined number of terminals for the camera slave unit 1 and the camera unit 3, and each of the camera units 3 has Terminal. Therefore, it is not possible to connect the camera devices 3 in excess of a predetermined number, and the input circuit for the video signal requires several terminals and the cost is high. And in the latter case, a door phone slave unit 1 with a camera
Is installed, only one camera device 3 can be connected to a predetermined connection terminal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a television intercom system capable of connecting a plurality of camera devices at low cost.

[0007]

According to a first aspect of the present invention, there is provided a television door phone system, comprising: a door intercom unit with a camera for outputting a video signal photographed by a television camera; a camera device; An intercom base unit with a television for inputting and displaying an image taken by the intercom base unit with a camera and a camera device. The intercom base unit with a television and the intercom base unit with a camera, and the intercom base unit with a television and a camera device. And a TV intercom system, each of which is connected by a two-wire balanced cable, wherein the camera device has an output impedance greater than a characteristic impedance of the two-wire balanced cable, and the camera device has at least two output impedances.
One of them is fed from the connection terminal of the intercom master unit with a television, and the other end of the connection is connected to a terminator having an impedance substantially equal to the characteristic impedance of the two-wire balanced cable. As a result, a plurality of camera devices are sent and connected from one connection terminal of the main unit of the intercom with a television.

According to a second aspect of the present invention, there is provided a door intercom system with a camera for outputting a video signal photographed by a television camera and a camera device, and a door intercom unit with a camera for inputting a video signal and a camera device. With an intercom master unit with a television and an intercom master unit with a television that projects the captured video, between the intercom master unit with a television and the intercom slave unit with a camera, and between the intercom master unit with a television and the camera device,
Are connected by a two-wire balanced cable, respectively, wherein the camera device and the intercom secondary master unit with the television have an output impedance larger than the characteristic impedance of the two-wire balanced cable, and the camera device and the interphone with the television are connected. The sub master unit is fed from the connection terminal of the intercom master unit with a television, and a terminator having an impedance substantially equal to the characteristic impedance of the two-wire balanced cable is connected to the end of this connection. . As a result, the camera device and the sub-unit with the intercom with the television are sent and connected from one connection terminal of the parent unit with the intercom with the television.

According to a third aspect of the present invention, the video intercom system of the first or second aspect further comprises a video receiving circuit of the main unit of the intercom with the television, and video signals from the sub unit with the camera and the camera device are inputted. It is supposed to be. As a result, the video signals from the camera device and the intercom slave unit with camera are input to the same video receiving circuit of the parent intercom unit with television.

According to a fourth aspect of the present invention, in the television door phone system, the feed connection according to the first or second aspect is made with two branches from the connection terminal. As a result, the camera device or the intercom sub-master device with the television is sent and connected to the two branches.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a television door phone system according to the present invention will be described with reference to FIGS.
A second embodiment will be described with reference to FIGS.

[First Embodiment] FIG. 1 is a system configuration diagram of a TV door phone system according to a first embodiment. FIG. 2 is a block diagram of a door phone slave unit with a camera of the TV door phone system shown in FIG. FIG.
2 is a block diagram of an intercom master unit with a television of the television door phone system shown in FIG. FIG. 4 is a block diagram of a video transmission circuit of the television intercom master unit shown in FIG. FIG. 5 is a block diagram of a video receiving circuit of the intercom master unit with a television shown in FIG. FIG. 6 is a block diagram of a camera device of the television door phone system shown in FIG.

This TV door phone system is installed in, for example, a house with a store, and includes a door phone slave unit with a camera (hereinafter, referred to as a camera slave unit) 1 and an intercom master unit with a TV (hereinafter, referred to as a master unit). 2 and a plurality of camera devices 3, wherein the parent device 2 and the camera child device 1 and the parent device 2 and the camera device 3 are respectively connected by a connection cable L which is a two-wire balanced cable. Is done. For example, two camera devices 3 are connected to the connection terminal 2 of the base unit 2.
v, and a terminator 5 having an impedance substantially equal to the characteristic impedance of the connection cable L is connected to the end of this connection.

The camera slave unit 1 is installed at an entrance or the like, and includes a television camera unit 1a for photographing a visitor and outputting a video signal, and a modulation circuit 1b for FM-modulating the video signal.
And a speaker 1c for outputting a voice from a living room, etc., and a microphone 1d for inputting a call voice and converting the voice into an electrical voice signal.
A receiving amplifier 1e for amplifying the audio signal and driving the speaker 1c, a transmitting amplifier 1f for amplifying the audio signal from the microphone 1d, and a 4-wire for performing the transmitting and receiving by a pair of wirings. 2-wire 4 to convert wiring to 2-wire wiring
A line conversion circuit 1g, a multiplexing circuit 1h for multiplexing a video signal and an audio signal to a power supply input, and a DC component as a power supply input from a multiplexed DC input supplied from the master unit 2, and 1, a power supply separation circuit 1i for supplying power to each circuit, a push button switch 1j used by a visitor to notify the visitor, and a multiplexed input having a non-polarized wiring connection. , And a pair of connection terminals 11 for connecting to the base unit 2.

The master unit 2 is installed in a living room of a house, and includes a demodulation circuit 2a for demodulating a video signal and a camera slave unit 1.
Alternatively, a monitor television unit 2b for displaying an image captured by the camera device 3, and a handset 2c having a speaker and a microphone for talking with the camera slave 1.
And a receiving amplifier 2d for amplifying the audio signal and driving the speaker of the handset 2c, and a transmitting amplifier 2e for amplifying the audio signal from the microphone of the handset 2c.
A two-wire / four-wire conversion circuit 2f for converting four-wire wiring into two-wire wiring so that transmission and reception can be performed by a pair of wirings; a video signal and an audio signal from the camera slave 1; A camera slave unit multiplexing circuit 2g for multiplexing an audio signal from the camera slave 2 to the camera slave unit 1 on two lines;
Unbalanced-balanced conversion transformer 2h for performing unbalanced-balanced conversion of connection wiring with the camera, buffer amplifier 2i for amplifying a video signal from camera slave unit 1, and a camera in a TV intercom system to which a sub master unit is connected. Call switch 2j for switching the communication path with slave 1 between master 2 and sub master
A push button operation detection circuit 2k for detecting that the push button switch 1j of the camera slave unit 1 is pressed; A monitor switch 21 used for the operation, a control signal modulation / demodulation circuit 2m, and a control circuit 2
n, a camera slave unit power supply superimposing circuit 2o for supplying power during standby and operation of the camera slave unit 1, and a power supply during standby and operation of the sub master unit in a TV intercom system to which the sub master unit is connected. Master power supply superimposing circuit 2p for supplying
Power supply circuit 2 for supplying power to each circuit of base unit 2
q, a multiplexing circuit 2r for the camera device and the sub master unit, a video transmission circuit 2s, a video reception circuit 2t, a pair of connection terminals 2u for connecting the camera slave unit 1, the camera device 3 and the sub master unit. It has a pair of connection terminals 2v for connecting the devices, and an AC power input 2w having, for example, a power plug for supplying AC power.

The control signal modulation / demodulation circuit 2m includes a camera device 3
And in the TV intercom system to which the sub master unit is connected, while modulating the control signal toward the sub master unit, and modulating the control signal output from the camera device 3 and the connected sub master unit. Demodulate.

The control circuit 2n is constituted by, for example, a one-chip microcomputer. The control circuit 2n is connected to the camera slave unit 1, the camera device 3, or the sub master unit together with the operation of each circuit of the master unit 2 based on a predetermined operation program. The operation of the sub master unit is controlled in the TV intercom system thus set. The control circuit 2n is provided with a push button switch 1j of the camera slave 1.
Push-button operation detection circuit 2k for detecting that the
The output signals from the control signal modulation / demodulation circuit 2m and the monitor switch 21 are input, and the operation of each circuit of the master unit 2 such as ON / OFF control of the monitor TV unit 2b, and the operation of the camera slave unit 1, the camera device 3, and the auxiliary master unit Is output to the control signal modulation / demodulation circuit 2m. Also,
When an operation switch (not shown) is operated, the control circuit 2n outputs a control signal including an address code for instructing the plurality of camera devices 3 to sequentially transmit video carriers and transmit video signals.

The camera device and the multiplex circuit 2r for the sub master unit are
The video doorphone system to which the video signal, the control signal, and the sub-base unit from the camera device 3 are connected separates the audio signal and the control signal from the sub-base unit from two lines, and
This is for multiplexing a control signal to the camera device 3 and a video signal, audio signal, and control signal from the master unit 2 to the sub master unit on two lines.

The video transmission circuit 2s is for transmitting a video signal from the camera slave unit 1 to the sub master unit when the sub master unit 4 described later is connected, and is connected to the connection terminal 2v. An unbalanced-balanced transformer TR for performing unbalanced-balanced conversion of a connection cable L to be connected, and a band-pass filter B
F, a transmission amplifier A1, and a switch S in which a resistor R0 for changing the output impedance when the connection system from the connection terminal 2v has one branch and two branches is connected in series. The resistance value of the resistor R0 is set to substantially the same value as the characteristic impedance of the connection cable L.

The transmission amplifier A1 converts a video signal to be transmitted into
This is for amplifying the output to a size receivable by the connected sub master unit and outputting the amplified signal. The output stage sets the output impedance of the frequency band of the video signal to be output to a value larger than the characteristic impedance of the connection cable L. For example, and is configured by a transistor, for example. The output impedance of the transmission amplifier A1 when the switch S is turned on has substantially the same value as the characteristic impedance of the connection cable L due to the combined resistance of the choke coil L and the resistor R0. Since the signal level is attenuated by half at the end of the connection cable to which the terminator 5 is connected, the amplification factor is set to twice at this end to ensure a predetermined signal level.

The video receiving circuit 2t is for receiving video signals from the camera slave unit 1 and the camera device 3, and includes a video transmitting circuit 2s, a camera device and a multiplexing circuit 2r for a sub master unit.
Therefore, video signals from the camera slave unit 1 and the camera device 3 are input. Then, as shown in FIG.
It comprises a balance-unbalance conversion transformer TR for performing balance conversion, a reception amplifier A2, and a band-pass filter BF. The reception amplifier A is for amplifying the received video signal to a size that can be demodulated by the demodulation circuit 2a. The band-pass filter BF is for removing a received signal other than a video signal transmission band that disturbs a video by the monitor television unit 2b.

The camera device 3 is installed in a room other than the place where the main unit 2 is installed in a store or a house, for example, and is a television camera unit for photographing the inside of the store and outputting a video signal. 3a, a modulation circuit 3b for FM-modulating a video signal, a control circuit 3c for controlling the operation of each circuit of the camera device 3, and a control signal from the control circuit 3c and a modulation signal from the master unit 2. A control signal modulation / demodulation circuit 3d for demodulating the control signal, a multiplexing circuit 3e, a power supply circuit 3f for supplying power to each circuit of the camera device 3, and a pair of power supply circuits for connecting to the base unit 2. It has a connection terminal 3g and an AC power input 3h that has a power plug and supplies AC power, for example.

The multiplexing circuit 3e is for multiplexing the video signal and the control signal into two lines, and is connected to the connection terminal 2v of the master unit 2 via the connection terminal 3g. And it is formed having an output impedance larger than the characteristic impedance of the two-wire balanced cable connected to the connection terminal 2v.

The control circuit 3c receives a control signal sent from the master unit 2, and checks a unique address number set by an address setting switch (not shown) or the like with an address code included in the control signal. . When the address code matches the unique address number, the output of the modulation circuit 3b is controlled to transmit a video signal. When the address code does not match the unique address number, or when a control signal for stopping the transmission of the video signal is input, the transmission of the video signal from the modulation circuit 3b is stopped.

The terminator 5 prevents the signal from being reflected at the end of the connection of the video signal output from the camera device by setting the impedance between the lines at the end of the connection terminal 2v to a predetermined value. This has a predetermined impedance substantially equal to the characteristic impedance of the connection cable L, that is, the two-wire balanced cable.

In the above configuration, the switch S of the video transmission circuit 2s of the base unit 2 is turned on, and the output impedance of the connection terminal 2v of the base unit 2 has substantially the same value as the characteristic impedance of the connection cable L. . The master unit 2 normally displays images from, for example, two camera devices 3 connected to the connection terminal 2v by the operation program of the one-chip microcomputer of the control circuit 2n at predetermined time intervals. The video of the camera slave unit 1 or the camera device 3 is switched by the operation of the monitor switch 2l. Then, the video signal is received by each TV camera unit by the video receiving circuit 2t, and the video is displayed on the monitor TV unit 2b, so that the resident can remotely monitor the store while staying there.
Then, when the push button switch 1j is operated by the visitor, the control circuit 2n switches the image to that of the camera slave unit 1 and projects the image, and the resident confirms the image of the visitor and makes a call.

According to the television doorphone system described above, a plurality of camera devices are sent and connected from one connection terminal of the main unit of the intercom with television.
The master unit 2 that can connect a plurality of camera devices 3 can be realized at low cost. In addition, a large space is not required for the terminal portion, so that a small intercom master unit with a television can be realized. Further, since the video signals from the camera device 3 and the camera slave unit 1 are input to the same video receiving circuit 2t of the master unit 2, the video receiving circuit can be shared, and therefore, the configuration is achieved at a lower cost. You can do it.

In the description of the above embodiment,
The number of camera devices to be connected is not limited to the one shown in FIG. Further, the video receiving circuit of the master unit is not limited to the one to which the video signals of the intercom slave unit and the camera device are input, and each of them may be input to another video receiving circuit.

[Second Embodiment] FIG. 7 is a system configuration diagram of a TV door phone system according to a second embodiment. FIG. 8 is a block diagram of an intercom secondary master unit with a television used in the television intercom system shown in FIG. FIG. 9 is a system configuration diagram of another embodiment related to the television door phone system of the second embodiment.

This television doorphone system has a first connection mode in which a television intercom master unit (hereinafter, referred to as a master unit) 4 is connected together with a camera device 3 together with a camera device 3 and a first connection configuration. This embodiment is different from the first embodiment, and the other components are the same as those of the first embodiment.

This TV door phone system is installed, for example, in a house with a store, and has a camera slave 1, a master 2, a camera device 3, and a sub master 4, and a base 2 and a camera slave 1 are provided. And the base unit 2, the camera device 3, and the sub-base unit 4 are connected by a connection cable L, which is a two-wire balanced cable. The camera device 3 and the sub master unit 4 are, for example, three camera devices 3 and one sub master unit 4 are sent and connected from the connection terminal 2v of the master unit 2 with two branches, and at the end of this connection. A terminator 5 having substantially the same impedance as the characteristic impedance of the connection cable L;
5 are respectively connected.

The sub master unit 4 is installed in a living room of a house, and includes a demodulation circuit 4a for demodulating a video signal from the camera slave unit 1 output from the main unit 2 or a video signal from the camera device 3. A monitor television unit 4 for displaying an image taken by the camera slave unit 1 or the camera device 3
b, a handset 4c having a speaker and a microphone for talking with the camera slave unit, a receiving amplifier 4d for amplifying an audio signal and driving a speaker of the handset,
A transmission amplifier 4e for amplifying an audio signal from the microphone of the handset, a two-wire / four-wire conversion circuit 4f for converting four-wire wiring to two-wire wiring for transmitting and receiving by a pair of wirings, A control signal modulating / demodulating circuit 4 h for modulating a control signal directed to master device 2 and demodulating a modulated control signal from master device 2;
A control circuit 4i for controlling the operation of each circuit of
The sub-base unit 4 is connected to a power supply separation circuit 4j for separating the DC component as a power supply from the multiplexed DC input supplied from the base unit 2 and supplying power to each circuit of the sub-base unit 4. And a pair of connection terminals 4k.

The control circuit 4i is composed of, for example, a one-chip microcomputer. The control circuit 4i detects a carrier signal or a synchronization signal of a video signal from the master unit 2 or the camera device 3 and detects a monitor signal based on the detection result of the control signal. Along with the operation of each circuit of the sub-base unit 4 such as the on / off control of the unit 4b, the control signal for controlling the operation of the camera slave unit 1 or the camera device 3 via the base unit 2 is output to the control signal modulation / demodulation circuit 4h. When an operation switch (not shown) is operated, the control circuit 4i instructs the camera slave unit 1 or the plurality of camera devices 3 to sequentially send out a video carrier and send out a video signal via the master unit 2. It has a function of outputting a control request signal including an address code of the camera device 3.

The multiplexing circuit 4g separates the video signal, the audio signal, and the control signal from the master unit 2 and multiplexes the audio signal and the control signal from the sub master unit 4 to the master unit 2 into two lines. Then, the connection terminal 2v of the base unit 2 is connected via the connection terminal 4k.
Connected to And it is formed having an output impedance larger than the characteristic impedance of the two-wire balanced cable connected to the connection terminal 4k.

In the above configuration, for example, the camera device 3 and the sub master unit 4 are sent and connected from the connection terminal 2v in different directions on the same floor in the building, or toward one of the same floor and the upper floor. Terminators 5 and 5 are connected to the ends of the connection. Then, the switch S of the video transmission circuit 2s of the base unit 2 is turned off, and the output impedance of the connection terminal 2v of the base unit 2 is set to a value larger than the characteristic impedance of the connection cable L.

The TV intercom system described above also includes:
The master unit 2 is operated, for example, by an operation program of a one-chip microcomputer of the control circuit 2n, for example. At normal times, for example, images from three camera devices 3 connected to the connection terminal 2v are projected at predetermined time intervals, or the resident operates the monitor switch 21 to activate the camera slave unit 1 or the camera device 3. Perform video switching. Then, the video signal is received by each TV camera unit by the video receiving circuit 2t, and the video is displayed on the monitor TV unit 2b, so that the resident can remotely monitor the store while staying there. Then, when the push button switch 1j is operated by the visitor, the control circuit 2n switches the image to that of the camera slave unit 1 and projects the image, and the resident confirms the image of the visitor and makes a call. Also, in the living room where the sub-base unit 4 is installed, the resident checks the image of the visitor with the sub-base unit 4 and makes a call by operating a predetermined switch. And so on. At this time, the resident can operate a predetermined operation switch to output a video signal to an arbitrary camera device 3 via the master device 2.

According to the TV intercom system described above, the camera device 3 and the sub master unit 4 are fed from one connection terminal of the master unit 2 and are connected to each other. Since the camera device 3 can be connected and the sub-base unit 4 can be connected to the same connection terminal, the sub-base unit 4 can be connected without providing a space for connecting the sub-base unit 4. Therefore, a small base unit 2 to which the sub-base unit 4 can be connected, which does not require a large space in the terminal portion, can be realized. In addition, the camera device 3 or the auxiliary master device 4
Is connected to the two branches, for example, when wiring is performed in different directions on the same floor in a building, or when wiring is performed toward one of the same floor and an upper floor, the wiring route of the connection cable L is changed. It can be formed in a simple shape, so that the loss of the video signal due to the wiring can be reduced and the workability is excellent. In addition, since the sub master unit 4 directly inputs a video signal from the camera slave unit 1 output from the master unit 2 or a video signal from the camera device 3 to project an image, the master unit 2 Only the video transmission circuit for the device 1 may be provided. Therefore, the sub-master device can transfer the video from the camera slave device 1 and the camera device 3 with the simple circuit configuration of the master device 2.

In the description of the above embodiment,
The present invention is not limited to the connection form and the number of connections of the camera device and the sub master unit, and for example, as shown in FIG. A connection form and an appropriate number may be sent and connected, such as a form in which one is connected one by one or a form in which one branch is a camera device and the other branch is a sub-base unit. Also,
The secondary master unit has been described by exemplifying the function of instructing a plurality of camera devices to send video signals through the master unit. However, the present invention is not limited to the function of the secondary master unit alone. A control signal may be sent to a plurality of camera devices by detecting the presence / absence of signal transmission to directly instruct sending of a video signal.

[0039]

According to the television intercom system of the first aspect, a plurality of camera devices are fed from one connection terminal of the intercom master unit with a television, so that a plurality of camera devices can be connected at a low cost. Intercom master unit with TV can be realized.

In the television intercom system according to the second aspect, the camera device and the intercom sub-master unit with the television are fed and connected from one connection terminal of the intercom master unit with the television. A main unit with a TV intercom that can connect multiple camera devices can be realized, and a sub-base unit with a TV can be connected to the same connection terminal. An intercom master unit with a TV that can be connected can be realized.

According to a third aspect of the present invention, in addition to the effects of the first or second aspect, in addition to the effects of the first or second aspect, the video signal from the camera device and the camera-equipped intercom slave unit is the same as that of the intercom master unit with the television. , The video receiving circuit can be shared, and therefore, the configuration can be made at a lower cost.

Further, in the television door phone system according to the fourth aspect, in addition to the effects of the first or second aspect, since the camera device or the sub-intercom unit with the television is connected to two branches and connected. In addition, the loss of the video signal due to the wiring can be reduced, and the workability is excellent.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a television door phone system according to a first embodiment of the present invention.

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

FIG. 3 is a block diagram of an intercom master unit with a television of the television intercom system shown in FIG. 1;

FIG. 4 is a block diagram of a video transmission circuit of the intercom master unit with a television shown in FIG. 3;

FIG. 5 is a block diagram of a video receiving circuit of the intercom master unit with a television shown in FIG. 3;

FIG. 6 is a block diagram of a camera device of the television door phone system shown in FIG.

FIG. 7 is a system configuration diagram of a TV door phone system according to a second embodiment.

FIG. 8 is a block diagram of an intercom sub-master with a television used in the television intercom system shown in FIG. 7;

FIG. 9 is a system configuration diagram of another embodiment related to the television doorphone system of the second embodiment.

FIG. 10 is a system configuration diagram of a conventional TV door phone system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intercom handset with camera 2 Intercom master unit with TV 2t Video receiving circuit 3 Camera device 4 Intercom master unit with TV 5 Terminator L 2-wire balanced cable

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Yoshihiro Tanikawa 1048 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd.

Claims (4)

[Claims] 1. A door phone slave unit with a camera and a camera device for outputting a video signal captured by a television camera,
An intercom base unit with a television for inputting a video signal and displaying an image taken by the intercom main unit with a camera and a camera device, and between the intercom main unit with a TV and the intercom main unit with a camera, and an intercom base unit with a TV And a camera device connected to each other by a two-wire balanced cable, wherein the camera device has an output impedance larger than a characteristic impedance of the two-wire balanced cable, and at least two of the camera devices are: A television doorphone system, wherein the television interphone system is fed from a connection terminal of the main unit with a television and is connected to a terminator having an impedance substantially equal to a characteristic impedance of the two-wire balanced cable at an end of the connection. . 2. An intercom with camera and a camera device for outputting a video signal photographed by a television camera,
An intercom master unit with a TV and an intercom sub master unit with a TV, which inputs a video signal and projects a video taken by a door phone slave unit with a camera and a camera device,
In a television intercom system in which a television intercom master unit and a camera intercom slave unit and a television intercom master unit and a camera device are respectively connected by a two-wire balanced cable, the camera device and the television intercom master unit are connected. The camera has an output impedance greater than the characteristic impedance of the two-wire balanced cable, and the camera device and the intercom sub-master with television are fed from the connection terminal of the intercom master with television, and the connection is terminated. And a terminator having an impedance substantially equal to the characteristic impedance of the two-wire balanced cable is connected to the video doorphone system. 3. The television according to claim 1, wherein a video signal from the intercom slave unit with camera and a camera device is input to the video reception circuit of the parent unit with television. Door phone system. 4. The method according to claim 1, wherein the feed connection is connected to the connection terminal by two.
3. The method according to claim 1, wherein the branch is performed.
The described TV door phone system.