JPH08163548A - Video door phone set - Google Patents

Abstract

PURPOSE: To install plural camera slave sets used to send a video signal, a voice signal and a call signal onto a common bus connecting to a master set. CONSTITUTION: A master set MQ1 and plural camera slave sets PQ1 to PQ8 are connected by common buses L1 to L6 through which a video signal f1 , a voice signals f2 and a call signal f3 are sent. Each video camera 1 is connected to the common video buses L1 , L2 , via a constant circuit means 6 and termination R1 , R2 are provided respectively to the ends of the common video buses L1 , L2 . Furthermore, each slave set microphone 2 is connected to the common video buses L1 , L2 , via a constant current circuit means 7 and a terminator R3 is provided to the end of the common video buses L1 , L2 . Furthermore, each DTMF generator (call signal generating circuit) 12 is connected to the common data buses L5 , L6 via a constant current circuit means 13 and a terminator R5 is provided to the end of the common data buses L5 , L6 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TV intercom system, and more particularly to a TV intercom system for connecting a master unit and a camera slave unit by a common two-wire system.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a surveillance television camera device capable of preventing the influence of standing waves without using a star type wiring (Japanese Patent Application No. 6-237764).
As shown in FIG. 5, in this surveillance television camera device, a plurality of surveillance cameras PQ _{11 to} PQ ₁₈ are provided, for example, common 6 lines L _{11 to} L.
It is connected in parallel to the master device MQ ₁₁ at ₁₆ .

The surveillance cameras PQ _{11 to} PQ ₁₈ are equipped with a surveillance camera unit 41 for picking up an image of a visitor and a power supply circuit 42 for driving the surveillance camera unit 41. The monitoring camera unit 41 is connected to a video signal modulation circuit 43 that outputs a video signal f _1, and the video signal modulation circuit 43 changes the output current according to the video signal f ₁ by a constant current circuit means 4.
4, the constant current circuit means 44 is a capacitor C
_The image terminals T ₃₁ and T ₃₂ are connected via ₁₃ and C ₁₄ . Further, the power supply side of the surveillance camera unit 41 is connected to a power supply circuit 42, and this power supply circuit 42 has power supply terminals T ₃₃ , T
Connected to ₃₄ . Further, the power supply circuit 42 is connected to the digital comparator 46 to which the number setting switch 45 is connected, and the digital comparator 46 receives the D signal from the input signal.
DTMF for extracting TMF signal and converting it to digital signal
The DTMF receiver 47 is connected to the receiver 47, and the DTMF receiver 47 is connected to the data terminals T ₃₅ and T ₃₆ .

Video terminals T ₃₁ , T ₃₂ , power supply terminals T ₃₃ , T ₃₄
The data terminals T ₃₅ and T ₃₆ are respectively connected to common video buses L ₁₁ and L ₁₂ of the common 2-wire system, common power supply buses L ₁₃ and L _14, and common data buses L ₁₅ and L ₁₆ . A television monitor 48 base unit MQ ₁₁ is to monitor the images from the monitoring camera unit 41 of the monitoring camera PQ ₁₁ ~PQ _18, a camera power supply circuit 49 supplies power to the monitoring camera unit 41, the monitoring camera PQ ₁₁ ~PQ ₁₈ And a ten-key pad 50 for individually calling

The monitor camera unit 4 is displayed on the TV monitor 48.
A common video bus L ₁₁ , to monitor the video from
The common video terminals T ₂₁ and T ₂₂ connected to L ₁₂ are balanced and unbalanced conversion coils 5 via capacitors C ₁₁ and C ₁₂ , respectively.
Connected to 1. This balanced / unbalanced conversion coil 51
The output side of is connected to the television monitor 48 via the video signal demodulation circuit 52.

The camera power supply circuit 49 is a common power supply bus L ₁₃ ,
It is connected to the common power supply terminals T ₂₃ and T ₂₄ connected to L ₁₄ . The numeric keypad 50 is connected to common data terminals T ₂₅ and T ₂₆ connected to the common data buses L ₁₅ and L ₁₆ via a DTMF generator 53. The DTMF generator 53 is connected to the DTMF receiver 54, and the DTMF receiver 54 is connected to the decoder 55. Decoder 5
5 is a surveillance camera PQ ₁₁ called by the ten key 50.
In order to monitor the image of the surveillance camera unit 41 of any one of the PQ _{18 on} the television monitor 48,
8 is connected.

[0007] Termination resistors R ₁ and R ₂ for converting the output current into a voltage are provided at both ends of the common video buses L ₁₁ and L ₁₂ . In thus configured surveillance television camera device, when to select a numeric keypad 50, for example, surveillance cameras PQ ₁₁ in the base unit MQ _11, corresponding to the surveillance camera PQ ₁₁ D
The TMF signal is output from the DTMF generator 53,
It is input to the common data terminals T ₃₅ and T ₃₆ of the monitoring camera PQ ₁₁ via the common data buses L _{15 to} L ₁₆ . The DTMF signal is converted into a digital signal by the DTMF receiver 47 of the surveillance camera PQ ₁₁ , compared with the own station number preset in the number setting switch 45, and if they match, the power supply circuit 42 is driven and the surveillance camera unit 41. The camera power is supplied to.

Surveillance camera unit 4 operated by this
The video signal input from the first camera eye 41a is FM-modulated by the video signal modulation circuit 43 and sent from the constant current circuit means 44 to the common video buses L ₁₁ and L ₁₂ . The video signal sent from the constant current circuit means 44 to the common video buses L ₁₁ and L ₁₂ is demodulated by the video signal demodulation circuit 52 of the parent device MQ ₁₁ , and can be monitored by the television monitor 48.

[0009]

However, since such a surveillance television camera device cannot transmit audio, it is not possible to monitor audio simultaneously with video. Therefore, the call between the master device MQ ₁₁ and the monitor cameras PQ _{11 to} PQ ₁₈ could not be performed by this monitor TV camera device.

Further, the monitor TV camera device could not call the master device MQ ₁₁ from the monitor cameras PQ _{11 to} PQ ₁₈ .

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and a plurality of video signals, audio signals and ringing signals are transmitted on a common bus connected to a master unit. An object is to provide a TV intercom device in which a camera slave unit can be installed.

[0012]

The television door intercom apparatus of the present invention that achieves the above object has a television camera, a television camera, and a common bus for transmitting a video signal, an audio signal and a calling signal.
A child speaker used for a call, a child microphone, a plurality of cameras having a calling signal generation circuit, a TV monitor for monitoring video signals from a child camera and a TV camera, a parent speaker used for a call, a parent having a parent microphone. Connected to the common bus via constant current circuit means for changing the output current according to the video signal of each television camera, and terminating resistors for converting the output current into a voltage are provided at both ends of the common bus, respectively. The slave microphone is connected to the common bus via the constant current circuit means that changes the output current according to the audio signal,
A terminating resistor for converting the output current into a voltage is provided at the end of the common bus, and each calling signal generating circuit is connected to the common bus via the constant current circuit means for changing the output current according to the calling signal to convert the output current into a voltage. A terminating resistor is provided at the end of the common bus.

Further, in the TV door intercom apparatus of the present invention, the constant current circuit means for changing the output current of the TV camera according to the video signal is provided between the constant current circuit to which the video signal is input, the constant current circuit and the terminating resistor. The impedance seen from the common bus to each surveillance camera side by n ² times (n ²
Is an integer of 2 or more).

Further, in the TV intercom apparatus of the present invention, the constant current circuit means for changing the output current of the TV camera in accordance with the video signal is composed of two sets of constant current circuits which receive the video signal and operate in opposite phases to each other. The impedance seen from the common bus to each surveillance TV camera side is n ² times (n is an integer of 2 or more) interposed between two sets of constant current circuits and terminating resistors.
It has a balun transformer.

[0015]

When transmitting the images from the television cameras of the plurality of camera slave units to the television monitor of the master unit, the image signals output from the television cameras of the plurality of camera slave units are transmitted via the constant current circuit means. Input from the common bus to the TV monitor of the base unit. At this time, the video signal is converted into a balanced current by the constant current circuit and output to the common bus, and the video signal output as a current is converted into a voltage by the terminating resistors connected to both ends of the common bus. As a result, the image from the TV camera can be displayed clearly on the TV monitor of the parent device.

In the case of transmitting audio signals from the slave microphones of a plurality of camera slaves to the master speaker of the master,
Audio signals output from the slave microphones of a plurality of camera slave units are input to the master unit speaker of the master unit from the common bus via the constant current circuit means. At this time, the audio signal is converted into a current by the constant current circuit and output to the common bus, and the audio signal output as a current is converted into a voltage by the terminating resistor connected to the end of the common bus. This allows the master unit speaker of the master unit to utter the voice from the slave unit microphone.

Further, when the call signals from the call signal generation circuits of the plurality of camera slave units are transmitted to the master unit speaker of the master unit, the call signals output from the call signal generation circuits of the plurality of camera slave units are transmitted. Input from the common bus to the master speaker of the master via the constant current circuit means. At this time, the calling signal is converted into a current by the constant current circuit and output to the common bus, and the calling signal output as a current is converted into a voltage by the terminating resistor connected to the end of the common bus. This allows
It is possible to cause the master unit speaker of the master unit to ring the ringing sound from the calling signal generation circuit.

If a balun transformer is provided on the output side of the constant current circuit that changes the output current of each television camera according to its video signal, the output power of the constant current circuit according to the video signal is boosted and each television camera is viewed. The output impedance can be increased. Further, if two sets of constant current circuits that receive video signals and operate in opposite phases to each other are provided, common-mode signals are removed and are less susceptible to common-mode noise.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the TV door intercom apparatus of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the TV intercom apparatus of the present invention has a plurality of camera slave units PQ.
_{1 to} PQ ₈ are common video buses (common audio buses) L ₁ and L ₂ ,
Common buses (common 6 lines) L _{1 to} L ₆ composed of common power supply buses L ₃ and L ₄ and common data buses L ₅ and L ₆ are connected in parallel to master device MQ ₁ .

The camera slave units PQ _{1 to} PQ ₈ have a television camera 1 for picking up an image of a visitor, a slave unit microphone 2 and a slave unit speaker 3 for talking with the master unit MQ ₁ , and a TV camera 1 and a slave unit speaker 3. PNP transistor 4 for driving
It has and. The television camera 1 is connected to a video signal modulation circuit 5 that outputs a video signal f _1, and the video signal modulation circuit 5 is connected to a constant current circuit means 6 that changes an output current according to the video signal f ₁ and a constant current circuit means 6 Is the capacitor C
_The video terminals T ₁₁ and T ₁₂ are connected via ₁ and C ₂ .

The constant current circuit means 6 includes a constant current circuit 32 to which a video signal f ₁ is input, as shown in FIG.
Constant current circuit 32 and termination resistors R ₁ and R ₂ (shown in FIG. 1)
Between the common video buses L ₁ and L ₂ of each camera slave unit P.
It is provided with a balun transformer BA _{1 for} quadrupling the impedance on the Q _{1 to} PQ ₈ side. The input side of the constant current circuit 32 is connected to the video signal modulation circuit 5 that outputs the video signal f _1, and the output side of the constant current circuit 32 is the balun transformer BA ₁
Of the coils L _A and L _C and coils L _D and L _B. The coils L _A and L _D are connected to the video terminals T ₁₁ and T ₁₂ , respectively, and the coils L _B and L _C are connected to the power source + B.

In addition, the balun transformer BA ₁ is generally connected from the common video buses L ₁ and L ₂ to the respective camera slave units PQ _{1 to} PQ.
N ² times the impedance seen from the Q ₈ side (n is an integer of 2 or more)
It may be one that does. Further, as shown in FIG. 3, the constant current circuit means 6 includes a phase shifter 33 to which the video signal f ₁ is input.
, Two sets of constant current circuits 34a and 34b to which the output of the opposite phase from the phase shifter 33 is input, and two sets of constant current circuits 34
a, 34b, and terminating resistors R ₁ and R ₂ (shown in FIG. 1) interposed between the common video buses L ₁ and L ₂ to the respective camera slave units PQ _{1 to} PQ _1.
It is provided with a balun transformer BA ₂ which increases the impedance when viewed from the Q ₈ side by a factor of 4.

The input side of the inverter 33a of the phase shifter 33 is connected to the video signal modulation circuit 5 which outputs the video signal f _1, and the output side of the inverter 33a is connected to the constant current circuit 34b. The output side of the inverter 33a is connected to the constant current circuit 34a via the inverter 33b. The constant current circuit 34a is an NPN transistor Q
_{1 to} Q ₄ , the collector of the NPN transistor Q ₁ is connected to the inverter 33b, and the emitter is NPN.
-Type transistor Q ₂ is connected to the reference potential point via the collector and emitter. The collector of the NPN transistor Q ₁ is connected to the base, and this base is connected to the base of the NPN transistor Q ₃ . The emitter of the NPN type transistor Q ₃ is connected to the reference potential point via the collector and emitter of the NPN type transistor Q ₄ . The base of NPN transistor Q ₂ is connected to the base and collector of NPN transistor Q ₄ .

The constant current circuit 34b is constituted by the NPN transistor Q ₁ to Q _4, the collector of an NPN transistor Q ₃ are connected to the inverter 33a, an emitter NP
It is connected to the reference potential point via the collector and emitter of the N-type transistor Q ₄ . NPN type transistor Q ₃
The collector of is connected to the base, which is connected to the base of the NPN transistor Q ₁ . The emitter of the NPN transistor Q ₁ is an NPN transistor Q ₂
Is connected to the reference potential point via the collector and emitter. The base of the NPN transistor Q ₂ is connected to the emitter of the NPN transistor Q _{1 and} the base of the NPN transistor Q ₄ .

Further, the NP provided in the constant current circuit 34a
The collector of the N-type transistor Q ₃ is a balun transformer B.
A ₂ is connected to the coils L _A and L _C , and a constant current circuit 34
The collector of NPN type transistor Q ₁ provided b is connected to the coil LD and L _B of the balun transformer BA _2. Coils L _A and L _D are connected to the video terminal T ₁₁ and T1 _2, respectively, the coil L _B and L _C is connected to the power supply + B.

Note that the balun transformer BA ₂ is generally connected from the common video buses L ₁ and L ₂ to the camera slave units PQ _{1 to} PQ.
N ² times the impedance seen from the Q ₈ side (n is an integer of 2 or more)
It may be one that does. As shown in FIG. 1, a coil L _E is connected between the video terminal T ₁₁ and the capacitor C ₁ , and this coil L _E is connected to the slave unit microphone 2 via the constant current circuit means 7. Video terminals T _12, the coil L _F is connected between the capacitor C _2, the coil L _F is connected to a reference potential point.

The power source side of the television camera 1 is connected to the collector of the PNP type transistor 4, and the emitter of this PNP type transistor 4 is connected to the power source terminal T ₁₃ . The collector of the PNP transistor 4 is connected to the slave speaker 3 via the capacitor C ₃ . The power supply terminal T ₁₄ is connected to the reference potential point. PN
The base of the P-type transistor 4 is connected to the digital comparator 9 to which the number setting switch 8 is connected, and the digital comparator 9 receives the DTMF (Dual T
It is connected to the DTMF receiver 10 which takes out the one multi frequency signal and converts it into a digital signal. The DTMF receiver 10 is connected to the data terminal T ₁₅ . A DTMF generator 12, which is a calling signal generating circuit connected to the calling button 11, is connected to the data terminal T ₁₅ via a constant current circuit means 13. The data terminal T ₁₆ is connected to the reference potential point.

The main unit MQ ₁ is a television monitor 14 for monitoring the images from the television cameras 1 of the camera slave units PQ _{1 to} PQ _8.
And a camera power supply circuit 1 for supplying power to the TV camera 1.
5, and a ten key 16 that can be called a Kamerako machine PQ ₁ ~PQ ₈ individually, a parent device microphone 17 and the master unit speaker 18 for a call with the Kamerako machine PQ ₁ ~PQ _8.

In order to monitor the video from the TV camera 1 on the TV monitor 14, common video terminals T ₁ and T ₂ connected to the common video buses L ₁ and L ₂ are connected via capacitors C ₄ and C ₅ , respectively. It is connected to the balanced / unbalanced conversion coil 19. The output side of the balanced / unbalanced conversion coil 19 is connected to the video signal demodulation circuit 20.
0 is connected to the television monitor 14 via the video amplifier 21. Common video terminal T1, the coil L _G is between the capacitor C _4, the hook switch 22 via the capacitor C ₆ is connected, the hook switch 22 is connected to the master unit speaker 18 via a receiver amplifier 23. The capacitor C _6, is between the hook switch 22 is connected terminating resistor R _3, the terminating resistor R ₃ is connected to the reference potential point. The common video terminal T _2, the coil L _H is connected between the capacitor C _5, the coil L _H is connected to a reference potential point.

The camera power supply circuit 15 includes a common power supply bus L ₃ ,
A common power supply terminal T ₃ of the common power terminal T _3, T _4, which is connected to L _4, are connected through the NPN type transistor 24. The collector of the NPN type transistor 24 is connected to the camera power supply circuit 15, the emitter of the NPN type transistor 24 is connected to the common power supply terminal T _3, the base of an NPN transistor 24 is connected to the resistor R _4, the resistor R ₄
Is connected to the reference potential point. Further, a hook switch 22 is connected between the base of the NPN transistor 24 and the resistor R ₄ via a capacitor C _7.
2 is connected to the master microphone 17 via the transmission amplifier 25. The common power supply terminal T ₄ is connected to the reference potential point.

The numeric keypad 16 is a DTMF generator 26.
And the DTMF generator 26 is connected to
7 via connected to the terminating resistor R _5, the common data terminal T ₅ terminating resistor R ₅ is connected to the common data bus L _5, L _6,
It is connected to the common data terminal T ₅ of T ₆ . The DTMF generator 26 thus connected is connected to the DTMF receiver 28, and the DTMF receiver 28 is connected to the decoder 29. The common data terminal T ₆ is connected to the reference potential point. Further, the DTMF receiver 28 is connected to a ringing tone generating circuit 32, and this ringing tone generating circuit 32 is connected between the receiving amplifier 23, the base unit speaker 18, and the DTMF generator 26.

The decoder 29 is connected to the television monitor 14 in order to monitor the image of the television camera 1 of any one of the camera slave units PQ _{1 to} PQ ₈ called by the ten key 16 on the television monitor 14. Also, the decoder 29
Is connected to the base of the NPN transistor 30 via the resistor R _6, and the collector of the NPN transistor 30 is L
The LED 31 is connected to the ED 31, and the LED 31 is connected to the power supply Vcc via the resistor R ₇ . NPN transistor 30
The emitter of is connected to the reference potential point. Resistance R ₆ ,
Between the base of the NPN type transistor 30 is connected to the resistor R _8, the resistor R ₈ is connected to the reference potential point.

Incidentally, terminal resistors R ₁ and R ₂ for converting the output current into a voltage are provided at both ends of the common video buses L ₁ and L ₂ . The operation of the TV door intercom apparatus thus configured will be described below. For example images from the TV camera 1 of Kamerako machine PQ ₁ to monitor the TV monitor 14 of the base unit MQ ₁ calls the TV camera 1 by the tuning operation of the ten key 16 of the base unit MQ _1. Specifically, by pressing the tuning button of the ten key 16 corresponding to the slave number of the camera slave PQ ₁ , the DTMF generator 26 outputs D as a tuning signal corresponding to the ten key 16.
The TMF signal f ₅ is output. The DTMF signal f ₅ is sent to the DT of the camera slave unit PQ ₁ via the common data buses L ₅ and L _6.
The digital comparator 9 receives the MF receiver 10.
Is input as a 4-bit digital signal.

The input digital signal is compared with the slave unit number set by the slave unit number setting switch 8 in the digital comparator 9, and when they match, the PNP transistor 4 is turned on by the digital comparator 9 and the master unit MQ. _Since the power supply for camera operation is supplied from the camera power supply circuit 15 of 1 to the TV camera 1, the TV camera 1 starts shooting. The video signal output from the camera eye 1a of the television camera 1 is FM-modulated by the video signal demodulation circuit 5, and the constant current circuit means 6 outputs a balanced current to the common video buses L ₁ and L ₂ .

The constant current circuit means 6 as shown in FIG.
Then, when the video signal f ₁ is input, the current of the constant current circuit 32 changes. This current change is the balun transformer BA ₁
Since the output power boosted by the coil L _A and the coil L _D of the balun transformer BA ₁ is transmitted to the balun transformer BA ₁ , the output impedance seen from the television camera 1 side can be increased. Further, in the constant current circuit means 6 as shown in FIG. 3, when the video signal f ₁ is input, the outputs of the inverters 33a and 33b of the phase shifter 33 are out of phase and are sent to the constant current circuits 34a and 34b. It Constant current circuit 34a
And 34b of the NPN type transistors Q _{1 to} Q ₄ are NP
It has a function of outputting a current according to the base current of the N-type transistor Q ₁ , and the two sets of the constant current circuits 34a and 34b are driven in opposite phases to form a balanced output, and the common mode signal is removed. Since the output power boosted by the coil L _A and the coil L _D of the balun transformer BA ₂ is sent, the output impedance seen from the television camera 1 side can be increased.

The video signal f ₁ output as a current is supplied to the terminating resistor R ₁
Is converted to a voltage by the video signal demodulation circuit 20 and the video amplifier 21 and is amplified.
The image from the TV camera 1 of the camera slave unit PQ ₁ can be displayed on the screen. The master device MQ ₁ sends out the DTMF signal f ₅ to the camera slave device PQ ₁ and at the same time the DTMF receiver 2
The DTMF signal f ₅ is received at 8, the 4-bit digital signal output from the DTMF receiver 28 is decoded at the decoder 29, and the LED of the corresponding camera slave device PQ ₁ is received.
31 is turned on. At this time, when the hook switch 22 is closed, the audio signal f ₂ from the slave microphone ₂ is output as a current by the constant current circuit means 7. Audio signal f output as current
₂ is a common video bus L ₁ , L used as a common audio bus
The voltage is converted by the terminating resistor R ₃ via 2 and the sound on the camera slave unit PQ ₁ side can be heard from the master unit speaker 18.

When transmitting from the master microphone 17 of the master MQ ₁ , the audio signal f output from the master microphone 17 is transmitted.
₄ is superimposed on the camera power supply from the camera power supply circuit 15,
After the direct current component is cut off on the side of the camera slave unit PQ _1, it is output from the slave unit speaker 3. Next, a case where the master device MQ ₁ responds to a call from the camera slave device PQ ₁ will be described.

When the call button 11 of the camera handset PQ ₁ is pressed, the DTMF generator 12 sends the DTMF signal f ₃ as a call signal corresponding to the handset number set by the handset number setting switch 8 to the constant current circuit means 13. Output current. The current output DTMF signal f ₃ is voltage-converted by the terminating resistor R ₅ via the common data buses L ₅ and L _6, and is received by the DTMF receiver 28 of the master device MQ ₁ .
A 4-bit digital signal based on the DTMF signal f ₃ output from the DTMF receiver 28 is decoded by a decoder 29.
LED 31 of the corresponding camera slave device PQ ₁
Light up. At the same time, since the ringing tone generation circuit 32 is activated, the ringing tone is output from the master unit speaker 18.

Here, the LE which is being turned on by the ten key 16 is turned on.
When the child device number of D31 is input, the image from the television camera 1 of the camera child device PQ ₁ can be displayed on the television monitor 14 by the same operation as described above. Also, the ending talk,
When the monitor ends, the end button 16a of the ten-key pad 16
By pressing, DTMF with the meaning of "end call"
The signal is sent out. This DTMF signal is not set in any of the camera slave units PQ ₁ , and when it is sent, the PNP transistor 4 of the camera slave unit PQ ₁ is turned off, so that the standby state is restored.

As shown in FIG. 4, the television door intercom apparatus of this embodiment is thus current-driven for all the video signals f ₁ , audio signals f ₂ and calling signals f ₃ from the camera slave units PQ _{1 to} PQ _8. Since the signal is transmitted, the output impedance becomes sufficiently higher than that of the terminating resistors R ₁ , R ₃ , and R _5, and the common bus L ₁
Even if a large number of Kamerako machine PQ ₁ ~PQ ₈ is connected in parallel on ~L _6, less susceptible to reduced levels due to a decrease in the impedance viewed from Kamerako machine PQ ₁ ~PQ ₈ side.

In the present embodiment, the DTMF signal is used as the data signal for selecting and calling the channel, but the data signal is not limited to this and may be a data signal in another format. Further, although the audio signal f ₄ from the master device MQ ₁ is described as transmitting a baseband signal, the present invention is not limited to this, and the AM, FM modulation circuit, the camera slave devices PQ _{1 to} PQ _{8 are} provided on the master device MQ ₁ side. An audio signal can be transmitted by providing an AM demodulation circuit and an FM demodulation circuit on the side.

Further, in the present embodiment, a terminating resistor R ₃ is provided at one end of the common video buses L ₁ and L ₂ used as a common audio bus, and a terminating resistor R ₅ is provided at one end of the common data buses L ₅ and L _6. However, like the common video buses L ₁ and L ₂ , termination resistors may be provided at both ends.

[0043]

As is apparent from the above embodiments, according to the TV door intercom apparatus of the present invention, the common bus for transmitting the video signal, the audio signal and the calling signal is used for the TV camera and the slave unit used for the call. A speaker, a slave microphone, a plurality of camera slave units having a calling signal generation circuit and a TV monitor for monitoring video signals from the TV camera, a master speaker used for a call, and a master unit having a master microphone are connected to each other. The television camera is connected to the common bus via the constant current circuit means that changes the output current according to the video signal, and terminating resistors for converting the output current into voltage are provided at both ends of the common bus, and each slave microphone is used as the audio signal. Each calling signal is connected to the common bus via constant current circuit means for changing the output current by a signal, and a terminating resistor for converting the output current into a voltage is provided at the end of the common bus. The conventional monitoring television camera device is provided by connecting the generating circuit to the common bus via the constant current circuit means for changing the output current according to the calling signal and providing the terminating resistor for converting the output current into a voltage at the end of the common bus. Since the voice signal and the call signal from the camera slave unit can be multiplexed by current drive on the common bus of
Multiple camera slaves can be installed on a common bus.

Further, the constant current circuit means for changing the output current of the television camera according to the video signal is interposed between the constant current circuit to which the video signal is input and the constant current circuit and the terminating resistor, and each surveillance camera is connected from the common bus. By having a balun transformer that multiplies the impedance viewed from the side by n ² times, the output power of the constant current circuit due to the video signal rises, so that the impedance viewed from the camera slave side can be increased.

Further, the constant current circuit means for changing the output current of the television camera in accordance with the video signal is composed of two sets of constant current circuits which receive the video signal and operate in opposite phases, and two sets of constant current circuit and termination. By having a balun transformer that intervenes between resistors and multiplies the impedance of each surveillance TV camera side from the common bus by n ² times, the common-mode signal is removed and the output impedance of the constant current circuit due to the video signal rises. A clearer image can be obtained without the occurrence of standing waves due to mismatching.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a TV intercom device according to the present invention.

FIG. 2 is a block diagram showing constant current circuit means used in the TV door phone apparatus according to the present invention.

FIG. 3 is a block diagram showing another embodiment of the constant current circuit means used in the TV door intercom apparatus according to the present invention.

FIG. 4 is a diagram showing the relationship between signals used in the TV door intercom apparatus according to the present invention.

FIG. 5 is a block diagram of a surveillance television camera device.

[Explanation of symbols]

1 ... TV camera 1a ... Camera eye 2 ... Handset microphone 3 ... Handset speaker 6, 7, 13 ... Constant current circuit means 14. ··· TV monitor 17 ··· parent microphone 18 ··· speaker 32, 34a, 34b ··· constant current circuit L _{1 to} L ₆ ··· common bus R _{1, R 2, R 3,} R 5 ····· termination resistor BA _1, BA ₂ ······ balun transformer video signal · · · · · · f ₁ audio signals · · · · · · f ₂ call signal ······ f ₃

Claims (3)

[Claims] 1. A common bus (L _{1 to} L ₆ ) for transmitting a video signal (f ₁ ), an audio signal (f ₂ ) and a calling signal (f ₃ ),
TV camera (1), handset speaker (3) used for communication, handset microphone (2), calling signal generation circuit (12)
Parent having a plurality of Kamerako machine (PQ1～PQ ₈₎ and a television monitor for monitoring the video signal from the television camera (14), the master unit speaker to be used for the call (18), the base-microphone (17) having a Machine (MQ ₁ ), each of the television cameras is connected to the common bus via a constant current circuit means (6) for changing the output current according to the video signal, and a terminating resistor (for converting the output current to a voltage) is connected. R ₁ and R ₂ ) are respectively provided at both ends of the common bus, and each of the slave microphones is connected to the common bus via a constant current circuit means (7) that changes an output current according to its voice signal. Termination resistor (R ₃ ) for converting output current to voltage
Is provided at the end of the common bus, and each of the ringing signal generating circuits is connected to the common bus via a constant current circuit means (13) for changing the output current according to the ringing signal, and the terminal for converting the output current into a voltage. A TV intercom device, wherein a resistor (R ₅ ) is provided at the end of the common bus. 2. The constant current circuit means for changing the output current of the television camera according to the video signal thereof comprises a constant current circuit (32) to which the video signal is input, the constant current circuit and the terminating resistor (R). ₁ and R ₂ ), and the impedance seen from the common bus to each TV camera side is n ²
A balun transformer (BA ₁ ) that doubles (n is an integer equal to or greater than 2) is provided. 3. The constant current circuit means for changing the output current of the television camera in accordance with the video signal thereof is provided with two sets of constant current circuits which receive the video signal and operate in opposite phases.
a, and 34b), the two pairs of constant current circuit and the termination resistor (R _1, R ₂₎ of the impedance viewed each said TV camera from the common bus interposed between n ² times (n is 2 or more The television intercom apparatus according to claim 1, further comprising a balun transformer (BA ₂ ) that operates as an integer.