JPH09200736A - Doorphone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a doorphone system with which the hand set of cordless telephone is easily made into system. SOLUTION: A monitor television base unit A has a power supply superimposing circuit for superimposing DC power supply from the monitor television base unit A onto a video signal transmitted from a doorphone hand set C with camera and at extended monitor televisions B1 and B2 , the output signal of this power supply superimposing circuit transmitted from the monitor television base unit A is separated into the video signal and the DC power supply. Besides, the extended monitor televisions B1 and B2 have charging means for charging cordless telephone hand sets E1 and E2 based on the separated DC power supply. Further, the extended monitor televisions B1 and B2 have cordless telephone hand set switches 51 for setting the charging voltages of the cordless telephone hand sets E1 and E2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intercom system in which a house person can confirm a visitor at a plurality of places indoors by an image and can make a call with a visitor as well as an outside line call through a public telephone line. Is.

[0002]

2. Description of the Related Art Conventionally, a cordless telephone connected to an indoor monitor television base unit enables outside line calls and calls with intercom subunits. An intercom system is provided that allows confirmation and calling with guests. As shown in FIG. 8, a conventional intercom system includes a monitor TV master unit A ′ that is placed indoors and a monitor TV master unit A ′ that is placed at the entrance of a house and has a communication line L _{1 including a} two-wire balanced cable. Doorphone with camera C connected via
And a cordless telephone master unit D connected to the public telephone line L ₀ and connected to the monitor television master unit A ′ via a communication line L ₂ composed of a two-wire balanced cable, and another monitor television master unit A ′. The extension monitor television B ₁ ″ installed in the room and connected to the monitor television master unit A ′ through the communication line L ₃ including the two-line balanced cable and the extension monitor television B ₁ through the communication line L ₄ including the two-line balanced cable. _The extension monitor television B ₂ ″ connected to the monitor television master unit A ′ by connecting the feed wiring from ₁ ″ (see FIG. 11) and the cordless installations in the vicinity of the extension monitor televisions B ₁ ″ and B ₂ ″ respectively a telephone handset E _1, E _2, the charger F ₁ of the cordless telephone slave unit E _1, for E ₂ ', F _2' constructed out with. here, the charger F ₁ ', F _2' each is , Charging station 6 with charging terminals
1, 61 ', charging cables 60, 60', and charging power adapters 62, 62 '(hereinafter, AC adapter 6
2, 62 '), and the AC adapter 62 is connected to a commercial power source (not shown).

As shown in FIG. 9, a door intercom with a camera C has a speaker 3 and a transmitter for receiving a call for communicating with a cordless telephone master unit D or cordless telephone slave units E ₁ and E ₂ as a cordless telephone communication device. A voice including a speaking microphone 4, an amplifier for driving the speaker 3, an amplifier for amplifying the voice from the microphone 4, and a hybrid circuit for handling two signals of a transmission signal and a reception signal in a pair of transmission paths. A camera unit 1 having a transmission / reception circuit 5 and an imaging camera for imaging a visitor.
A modulator 2 for modulating a video signal from the camera unit 1, a call button 9 for calling a family member, and a call signal for transmitting the fact that the call button 9 is pressed to the monitor television main unit A ′. The calling signal generating circuit 8 that is generated, and the audio signal, the video signal, and the calling signal are multiplexed, and the monitor television master unit A '
A multiplexer / demultiplexer circuit 6 for transmitting power to the monitor TV master unit A ′ and separating the voice of the intercom call transmitted from the cordless phone master unit D or the cordless phone slave units E ₁ and E ₂ and A power supply circuit 7 for supplying DC power to each of the above parts based on the power supply from the monitor TV master unit A'separated by the separation circuit 6, and the monitor TV master unit A '.
And a diode bridge circuit 10 for making the connection terminal 11 nonpolar.

The monitor television base unit A'is shown in FIG.
Sea urchin communication line L₁Doorphone with camera connected to C
Video signals, audio signals, and ringing signals sent from
Door phone communication by cordless phone base unit D as it is released
Multiplex the power of the voice of the talk and the doorphone with camera
Demultiplexing circuit 22 and the demultiplexing circuit 22
Video signal from doorphone with camera
TV B₁"(Or B _TwoAmplify for transmission to
Amplifier 23 and additional monitor TV B₁"Or B _TwoTo
(In order to monitor the image of the intercom subunit C with camera
The monitor button 54 or 54 '(see FIG. 8) is pressed
At times, power is supplied to the intercom unit C with camera to activate it.
In order to do this, an additional monitor TV B multiplexed with the video signal
₁"Or B_TwoData for separating the monitor-on signal from
Signal separation circuit 25 'and additional monitor TV B₁”,
B_Two"Unbalanced-balanced for transmitting good video signal to
The conversion circuit 26 and the communication line L_ThreeAdditional monitor tv via
B₁, And a demultiplexing circuit 22
Video separated from (from the intercom with camera camera C)
Demodulator 28 for demodulating the signal, and demodulated by the demodulator 28
Monitor television that displays the video by processing the processed video signal
29 and presence / absence of a calling signal from the intercom subunit C with camera
A call signal detection circuit 30 for detecting the
Audio from the doorphone with camera subunit C separated by path 22
Unbalance for transmitting signals to the cordless telephone master unit D −
Balanced conversion circuit 33 and cordless telephone base unit D with camera
Call for notifying that the intercom slave C is being called
The output signal output circuit 34 and the cordless telephone master unit D
Doorphone response state detection circuit that detects whether or not
35, a connection end for connecting the cordless telephone master unit D
A mode for turning on / off the child 38 and the monitor TV 29.
Nita button 32 and signal processing based on the input signal
It is provided to the CPU 31 that controls the operation of each of the above-mentioned parts and the above-mentioned each part.
DC power supply to be supplied from commercial power supply (not shown)
The circuit 37 and the output of the power supply circuit 37 are connected to the doorphone with camera.
A switch 36 for supplying to the container C and a camera door
And a connection terminal 21 for connecting to the slave unit C.
I have. The cordless telephone master unit D is connected via the power cord.
Connected to a commercial power source (not shown).

As shown in FIG. 11, the extension monitor television B ₁ ″ has a connection terminal 41 for connecting to the monitor television master unit A ′ and a connection terminal 42 for connecting another extension monitor television B _2. , A balanced-to-unbalanced conversion circuit 44 for converting the video signal balanced-transmitted from the monitor television base unit A ′ into an unbalanced state, a monitor button 54 for monitoring the image of the intercom unit C with camera, and a monitor button 54. A data signal for notifying the CPU 31 of the monitor television main unit A ′ that the button has been pressed (this data signal is output from the CPU 52 ′ described later when the monitor button 54 is pressed) is multiplexed with the video signal. Data signal multiplexing circuit 45, a demodulator 46 for demodulating the video signal from the intercom sub-unit C with camera, and a monitor television for signal-processing and displaying the video signal demodulated by the demodulator 46. 47, a synchronous separation circuit 48 for determining the presence or absence of the video signal, the sync separation signal by sync separator 48 are input monitor television 47
On / off control performs CPU52 is constituted out with 'a commercial power supply circuit 49 which performs DC power supply to be connected to (not shown) expanded monitor television B ₁ "in the above units'. Incidentally, "the basic structure and operation of the additional monitor television B _1" additional monitor television B ₂ are the same as, additional monitor television B ₁ ", B _2" connection terminals 42, 42 ', when not connected to additional monitor TV Are short-circuited by the terminator 70.

[0006]

By the way, in the above doorphone system, additional cordless telephone handsets E ₁ and E _{2 are used.}
Chargers F ₁ 'and F ₂ ' for charging the AC adapter 6
2,62 'must be provided with a further, AC adapter 62, 62' must be connected to a commercial power source, also additional TV monitor B ₁ ", B _2" respectively is also connected to a commercial power source Since it is necessary, there is a problem that it is difficult to systematize the extension cordless telephone slave units E ₁ and E ₂ and the extension monitor TVs B ₁ ″ and B ₂ ″. Further, when the cordless telephone master set D or the cordless telephone sub-units E ₁ and E ₂ respond to the intercom subunit C with camera, the monitor television main unit A ′ and the extension monitor televisions B ₁ ″, B ₂ "All of the respective monitor televisions 29, 47, 47 'were turned on, and unnecessary monitor televisions could not be turned off.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an intercom system in which a cordless telephone master unit and a cordless telephone slave unit are easily systematized.

[0008]

In order to achieve the above object, the invention of claim 1 is an intercom subunit having an imaging camera, and the intercom subunit connected to the intercom subunit via a communication line. A monitor television that displays an image captured by the image capturing camera based on a video signal transmitted from the monitor camera, a monitor television master unit that includes a power supply circuit that is connected to a commercial power source and outputs a direct current power source, and the monitor television parent Monitor television which is connected to the monitor via a communication line and displays a video image picked up by the image pickup camera on the basis of a video signal transmitted from the monitor television base unit, and an extension monitor TV and a public telephone line. A cordless telephone master unit that is connected to the monitor television master unit through a communication line, and a cordless telephone slave unit that is wirelessly connected to the cordless telephone master unit Made, the monitor television base unit has a power superposition means for superimposing a direct current power from the power supply circuit to the transmitted video signal from the intercom slave unit,
Each of the additional monitor televisions has a separating means for separating an output signal of the power superimposing means transmitted from the monitor television main unit through a communication line into a video signal and a DC power supply, and a DC power supply separated by the separating means. Charging means for charging the cordless telephone handset based on, and a charging voltage setting means for setting the charging voltage of the cordless telephone handset, characterized in that, in the additional monitor TV, The cordless telephone subunit can be charged by the charging unit based on the DC power source separated by the separating unit, and the charging voltage of the cordless telephone subunit can be set by the charging voltage setting unit. The device can be integrated with an extension monitor TV, and the cordless telephone master unit and the cordless telephone slave unit can be easily systemized. Further, since it is not necessary to connect the additional monitor TV and the cordless telephone slave unit to the commercial power source, it is possible to increase the degree of freedom of the installation place of the additional monitor television and the cordless telephone slave unit.

According to a second aspect of the present invention, in the first aspect of the invention, the extension monitor television has an attachment / detachment detecting means for detecting attachment / detachment of the cordless telephone handset in the connected charging means. It is possible to determine whether or not the response is made by the cordless telephone handset. According to a third aspect of the invention, in the first aspect of the invention, the monitor television base unit and the additional monitor television are cordless telephone base units,
Since the cordless telephone slave unit has means for communicating the usage status of each cordless telephone slave unit, it is possible to turn off the monitor TV attached to the cordless telephone master unit and the cordless phone that are not responding to the intercom subunit.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
It will be described with reference to the drawings. FIG. 1 shows a system showing the present embodiment.
It is a system configuration diagram. This intercom system is shown in FIG.
Like a camera door attached to the entrance of a house
Communication device L, which consists of a two-wire balanced cable₁Through
Connect to the monitor TV base unit A located in one indoor room
And the intercom slave terminal of the cordless telephone master unit D
(Not shown) and monitor TV base unit A are 2-wire balanced cables
Communication line L_TwoConnected through. Cordet
Telephone main unit D is public telephone line L₀Is also connected to.
In addition, an additional monitor TV B installed in another room₁Is 2
Communication line L consisting of line balance cable_ThreeMonitor via
It is connected to the base unit A and has an additional monitor TV B._TwoIs two-wire equilibrium
Communication line L consisting of cable_FourBy add monitor tv
B₁Connected from the feed wire (see Fig. 4) Monitor TV parent
Connected to machine A. Wireless to cordless phone base unit D
Extension cordless telephone handset E to be connected ₁, E_TwoIs increased
Built-in monitor TV B₁, B_TwoCharging cable 60,6
0 ', which is connected through 0'and has a charging terminal
It is installed on the charging stand 61, 61 'for the telephone handset.

In this doorphone system, a visitor calls a call button.
When 9 is pressed, the cordless telephone master unit D rings and the family member
If you press the button 32, the communication line L₁Monitor tv parent through
From the machine A to the intercom unit C with camera
DC power is supplied for the camera unit.
The image of the visitors being driven by the communication line L₁By
Is transmitted to the monitor TV master unit A, and the monitor TV master unit A
Is displayed on the monitor television 29. Here, the family members
Door phone with camera if dress phone base unit D is hooked off
The intercom call can be made with the child device C. Also, expansion
Monitor TV B ₁Or B_TwoMonitor TV 47 or 4
Cordless telephone handset E while looking at the image of 7 '₁Or E_Two
It is also possible to talk to the doorphone with the camera-equipped doorphone subunit C
Noh.

FIG. 2 shows the configuration of the intercom subunit C with a camera.
However, since the configuration and operation are the same as the conventional example, the description is omitted.
You. As shown in FIG. 3, the monitor TV base unit A uses a communication line.
L₁From the intercom with camera-equipped intercom C connected via
Separate incoming video and audio signals and ringing signals
With the sound of the intercom call by the cordless phone master unit D
Multiplex the DC power supply to the voice / camera doorphone subunit C
Demultiplexing circuit 22 and demultiplexing circuit 22
The video signal from the doorphone subunit C with camera is added to the monitor screen.
Levi B₁(Or B_Two) Amplifier to amplify for transmission to
23 and (additional monitor TV B₁, B _TwoAt the code
Less phone cordless handset E₁, E_TwoAmplifier 23 to charge the
Power supply superimposition that superimposes DC power supply on the video signal amplified by
Circuit 24 and additional monitor TV B₁, B_TwoMoni at
Door phone with camera when the button 54, 54 'is pressed
Signals for supplying power to slave unit C and putting it in an operating state, expansion
Monitor TV B₁, B_TwoCordless phone attached to
Machine E₁, E_TwoOff-hook, etc. additional monitor TV B₁,
B_TwoExtension monitor TV B showing the usage status of₁, B_TwoFrom
Separates the received data signal of the
From A to additional monitor TV B₁, B_TwoData sent to
Data signal demultiplexing circuit 25 and the extension monitor tele
B₁, B _TwoUnbalance for transmitting good video signal to
-Balance conversion circuit 26 and communication line L_ThreeExpansion monitor via
TV B₁With a connection terminal 27 for connecting the
Demodulator 28 for demodulating the video signal from the intercom slave C
Signal processing the video signal demodulated by the demodulator 28
A monitor TV 29 for displaying images and a door phone with a camera
A ringing signal for detecting the presence or absence of a ringing signal from the slave unit C.
No. detection circuit 30 and a cordless telephone master unit D with a camera
Unbalanced for transmitting the audio signal from the Ahon phone C-
Balanced conversion circuit 33 and cordless telephone base unit D with camera
Call for notifying that the intercom slave C is being called
The output signal output circuit 34 and the cordless telephone master unit D
Doorphone response state detection circuit that detects whether or not
35, a connection end for connecting the cordless telephone master unit D
Turn on the child 38 and the monitor TV 29 of the monitor TV base unit A.
Monitor button 32 for turning on / off and input from the above parts
Signal processing and operation of each circuit
A CPU 31 for controlling and a direct drive for driving each of the above parts.
A power supply circuit 37 for generating a current source from a commercial power source (not shown)
And the output of the power supply circuit 37 to the intercom unit C with camera.
Switch 36 for feeding and door phone with TV C
And a connection terminal 21 for connecting. In addition,
As shown in FIG. 6, the monitor television base unit A includes a demodulator 28.
The video signal demodulated at
A sync separation circuit 48 for inputting a signal to the CPU 31 is provided.
It may be one.

As shown in FIG. 4, the extension monitor television B ₁ has a connection terminal 41 for connecting to the monitor television master unit A.
And a connection terminal 42 for connecting to another extension monitor TV B ₂ , and a signal for separating the video signal and data signal transmitted from the monitor TV master A into a DC power source and transmitting them to the monitor TV master A. Demultiplexing circuit 4 for multiplexing
3, a balanced-unbalanced conversion circuit 44 for converting the video signal and the like from the monitor TV base unit A separated by the demultiplexing circuit 43 into an unbalanced state, the state of the extension monitor TV B ₁ itself and the cordless telephone slave unit. For demultiplexing the data signal transmitted to the monitor television master unit A indicating the use state such as off hook of E _{1 and} the data signal indicating the state of the monitor television master unit A received from the monitor television master unit A from the video signal. Separated by the data signal demultiplexing circuit 45 and the data signal demultiplexing circuit 45 (from the camera-equipped intercom subunit C)
A demodulator 46 for demodulating a video signal, a monitor television 47 for processing the video signal demodulated by the demodulator 46 to display a video, a sync separation circuit 48 for determining the presence or absence of a video signal, and a synchronization The monitor television 47 is provided only when the signal separated by the separation circuit 48 is input and there is a synchronization signal.
CPU 52 for instructing to display an image on the monitor, a monitor button 54 for monitoring an image picked up by the intercom subunit C with a camera (in the additional monitor TV B ₁ ), and a cordless telephone subunit E ₁ for charging. The cordless telephone slave unit charging circuit 50, the charging voltage setting switch 51 which is the charging voltage setting means for setting the charging voltage to correspond to the cordless telephone slave unit E ₁ having various charging voltages, and the cordless telephone slave unit E ₁ A cordless telephone handset attachment / detachment detection circuit 53 which is attachment / detachment detection means for detecting an off-hook state,
It is configured with a connection terminal 55 for connecting a charging cable 60 connected to the charging stand 61, and the cordless telephone slave unit charging circuit 50 and the charging stand 61 constitute a charging means. The basic configuration and operation of the additional monitor television B ₂ is the same as the additional monitor television B _1, additional TV monitor B _1,
The connection terminals 42 and 42 ′ of B ₂ are short-circuited by the terminator 70 when the additional monitor TV is not connected.

In this doorphone system, the monitor TV parent
Machine A transmits the video signal transmitted from camera-equipped intercom subunit C.
Signal from the power supply circuit 37 inside the monitor TV base unit A.
It has a power supply superimposing circuit 24 that superimposes a current
TV B₁, B_TwoIs transmitted from the monitor TV base unit A.
The output signal of the incoming power superimposing circuit 24 is a video signal and a direct current.
Since it has a demultiplexing circuit 43 that separates the power supply,
Nita TV B₁, B_TwoNeed to be connected to a commercial power source
Yes. In addition, additional monitor TV B₁, B_TwoDemultiplexing times
Cordless telephone based on the DC power supply separated by path 43
Machine E₁, E_TwoCordless phone cordless handset charging circuit 5
Since it has 0, charging cable 60, charging stand 61
Cordless telephone handset E via₁, E_TwoTo charge
And has a charging voltage setting switch 51.
This allows cordless phone handsets with various charging voltages.
E₁, E_TwoCan be integrated. In addition,
Nita TV B₁, B_TwoCordless telephone cordless attachment detection
Since the circuit 53 is included,
-Dress phone cordless handset E₁, E_TwoCan be detected. here
Then, monitor TV base unit A, additional monitor TV₁, B_Two
Each has a data signal demultiplexing circuit 25, 45.
Then, cordless telephone master unit D, cordless telephone slave unit E ₁,
E_TwoMultiplexes the data signal indicating each usage state with other signals
It can be sent by sending it to the CPU 31, 52.
The unused ones of the monitor TVs 29, 47, 47 '
Can be controlled to turn off.

In the doorphone system shown in FIG. 1,
'Was the the additional monitor television B _1, B ₂ into another location, as shown in FIG. 5, the charging base 61, 61' charger 61, 61 so as to built-in expansion TV monitor B _1, B _2, The cordless telephone slave units E ₁ and E ₂ may be stored. Further, as shown in FIG. 7, the extension monitor television B ₁ , shown in FIG.
At B ₂ , the cordless telephone slave unit charging circuit 50 displays whether the cordless telephone slave units E ₁ and E ₂ are being charged or whether the charging is completed, for example, two-color light emitting diodes LED ₁ and LED ₂ By adding display elements such as the above, the charging states of the cordless telephone slave units E ₁ and E ₂ can be grasped.

[0016]

According to the invention of claim 1, the monitor television main unit has a power superimposing means for superimposing the DC power from the power circuit on the video signal transmitted from the intercom subunit.
The additional monitor TV includes a separating unit that separates an output signal of the power superimposing unit transmitted from the monitor TV master unit through a communication line into a video signal and a DC power supply, and a DC power supply separated by the separating unit. Since it has a charging means for charging the cordless telephone handset based on the base and a charging voltage setting means for setting the charging voltage of the cordless telephone handset, the extension monitor TV is separated by the separating means. The cordless telephone slave unit can be charged by the charging means based on the DC power source, and the charging voltage of the cordless telephone slave unit can be set by the charging voltage setting means. Therefore, the cordless telephone master unit and the cordless telephone slave unit can be easily systemized. Further, since it is not necessary to connect the additional monitor TV and the cordless telephone slave unit to the commercial power source, there is an effect that it is possible to increase the degree of freedom of the installation place of the additional monitor television and the cordless telephone slave unit.

According to a second aspect of the present invention, in the first aspect of the present invention, the extension monitor television has an attachment / detachment detecting means for detecting attachment / detachment of the cordless telephone handset in the connected charging means. There is an effect that it is possible to determine whether or not the response is made by the cordless telephone handset. According to the invention of claim 3, in the invention of claim 1, since the monitor television master unit and the additional monitor television each have means for communicating the usage status of each of the cordless telephone master unit and the cordless telephone slave unit, There is an effect that it is possible to turn off the monitor television attached to the cordless telephone base unit and the handset which are not responding.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an overall configuration of the present embodiment.

FIG. 2 is a schematic circuit configuration diagram of an intercom subunit with a camera according to the present embodiment.

FIG. 3 is a schematic circuit configuration diagram of a monitor television master unit according to the present embodiment.

FIG. 4 is a schematic circuit configuration diagram of an additional monitor television according to the present embodiment.

FIG. 5 is another system configuration diagram showing the overall configuration of the present embodiment.

FIG. 6 is a schematic circuit configuration diagram of a monitor television master unit according to the present embodiment.

FIG. 7 is a schematic circuit configuration diagram of an additional monitor television according to the present embodiment.

FIG. 8 is a system configuration diagram showing an overall configuration of a conventional example.

FIG. 9 is a schematic circuit configuration diagram of a camera-equipped doorphone subunit in a conventional example.

FIG. 10 is a schematic circuit configuration diagram of a monitor television master unit in a conventional example.

FIG. 11 is a schematic circuit configuration diagram of an extension monitor television in a conventional example.

[Explanation of symbols]

A Monitor TV base unit B ₁ , B ₂ Expansion monitor TV C Doorphone subunit with camera D Cordless telephone base unit E ₁ , E ₂ Cordless telephone subunit L ₀ Public telephone line L ₁ , L ₂ , L ₃ , L ₄ communication Line 29 Monitor television 32 Monitor button 54, 54 'Monitor button 47, 47' Monitor television 51 Charging voltage setting switch 60, 60 'Charging cable 61, 61' Charging stand

[Procedure amendment]

[Submission date] April 1, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

By the way, in the above doorphone system, additional cordless telephone handsets E ₁ and E _{2 are used.}
Chargers F ₁ 'and F ₂ ' for charging the AC adapter 6
2,62 'must be provided with a further, AC adapter 62, 62' must be connected to a commercial power source, also additional TV monitor B ₁ ", B _2" respectively is also connected to a commercial power source Since it is necessary, there is a problem that it is difficult to systematize the extension cordless telephone slave units E ₁ and E ₂ and the extension monitor TVs B ₁ ″ and B ₂ ″. Further, when the cordless telephone master set D or the cordless telephone sub-units E ₁ and E ₂ respond to the intercom subunit C with camera, the monitor television main unit A ′ and the extension monitor televisions B ₁ ″, B ₂ "Each monitor TV 29, 47, 47 ' is turned on ,
I could not turn off unnecessary monitor TVs.

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

Claims (3)

[Claims] 1. An intercom subunit having an imaging camera,
A monitor TV that is connected to the intercom sub-unit via a communication line and displays an image captured by the imaging camera based on a video signal transmitted from the intercom sub-unit, and is connected to a commercial power source and outputs a DC power source. And a video image captured by the imaging camera based on a video signal transmitted from the monitor television master unit, which is connected to the monitor television master device via a communication line, and which is equipped with a power supply circuit. An additional monitor TV having a monitor TV for displaying, a cordless telephone master unit connected to a public telephone line and connected to the monitor television master unit via a communication line,
And a cordless telephone slave unit wirelessly connected to the cordless telephone master unit, wherein the monitor television master unit superimposes a DC power source from the power supply circuit on a video signal transmitted from the intercom subunit. Each of the additional monitor televisions has a separating means for separating an output signal of the power superimposing means transmitted from the monitor television main unit through a communication line into a video signal and a DC power source, and the separating means. An intercom system comprising: a charging unit that charges the cordless telephone slave unit based on the generated DC power source; and a charging voltage setting unit that sets a charging voltage of the cordless telephone slave unit. 2. The intercom system according to claim 1, wherein the extension monitor television includes an attachment / detachment detection means for detecting attachment / detachment of the cordless telephone slave unit in the connected charging means. 3. The intercom system according to claim 1, wherein each of the monitor television main unit and the additional monitor television is provided with means for communicating a use state of each of the cordless telephone master unit and the cordless telephone slave unit.