JP2667311B2 - TV door phone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to transmit a video signal from an intercom slave unit installed at an entrance or the like to an intercom master unit installed indoors so that visitors can be visually checked by the intercom master unit. And a television doorphone device.

[0002]

2. Description of the Related Art Conventionally, a video signal is transmitted from an intercom slave unit installed at an entrance or the like to a master intercom unit installed indoors so that visitors can be visually checked by the intercom master unit. Doorphone devices are used. FIG. 4 shows a block diagram of a conventional TV door phone apparatus.

In FIG. 4, a door phone master unit 401 provided indoors is connected via a communication cable L to a door phone slave unit 402 provided at an entrance or the like. The handset master unit 401 includes a handset 403 and a monitor TV 40.
4 are provided. On the other hand, in the door phone handset 402,
TV camera 405, microphone 406, and speaker 40
7 are provided.

A video signal, an audio signal, and a DC power supplied from a door phone master unit 401 as a drive power source for the door phone slave unit 402 are superimposed and transmitted to the communication cable L. In the conventional television intercom apparatus configured as described above, the visitor is photographed by the television camera 405 and the video signal is transmitted to the intercom master unit 401 via the communication cable L. A display corresponding to the video signal is displayed on the monitor television 404 of the intercom base unit 401.

[0005] Further, a telephone call is made by the handset 403 of the intercom master unit 401, the microphone 406 and the speaker 407 of the intercom slave unit 402, and the audio signal at this time is transmitted via the communication cable L. As described above, while visually confirming the visitor with the intercom base unit 401,
A call can be made with the intercom slave unit 402.

[0006]

In the above-described conventional television door phone apparatus, a video signal, an audio signal, and a power supply for driving the door phone slave unit 402 are shared by a common communication cable L.
, The configuration can be simplified. By the way, the power transmitted from the intercom master device 401 to the intercom slave device 402 to drive the television camera 405 is a DC signal, and the driving power supply voltage of the television camera 405 requires a relatively high voltage. Therefore, when the length of the communication cable L becomes longer, a voltage drop occurs in the power supply due to the line resistance of the communication cable, so that the television camera 405 cannot be driven. Therefore, there is a problem that it is difficult to dispose the doorphone master unit 401 and the doorphone slave unit 402 at a desired position with a distance therebetween.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a television door phone apparatus in which a power supply voltage for driving a television camera does not decrease even when a communication cable becomes long.

[0008]

In order to achieve this object, a television intercom apparatus according to the present invention comprises an AC signal generating circuit,
A mixer that mixes and modulates an output signal of an AC signal generation circuit with an audio output signal of a microphone, an output unit that outputs a modulated output signal from the mixer to a communication cable, and demodulates a video signal received via the communication cable. Intercom main unit equipped with a video signal demodulation circuit to perform and a monitor television for displaying an output signal of the demodulation circuit as a video signal, a DC power supply for rectifying a modulated signal from a mixer received via a communication cable to generate a DC power supply Means and a speaker driven by a DC power source, for outputting a demodulated audio signal from the DC power source means,
An intercom unit having an image pickup unit for transmitting a video signal to a communication cable and an amplification circuit for amplifying an audio signal output from a microphone and transmitting the audio signal at a baseband to the communication cable, and the intercom master unit is connected via the communication cable. And a speaker for outputting a baseband audio signal received.

[0009]

The alternating-current signal from the alternating-current signal generating means of the intercom master unit is converted into a direct-current power supply by the direct-current power supply means in the intercom slave unit, and is used as the direct-current power supply for the imaging means and the upstream audio signal amplification circuit. On the other hand, the AC signal from the AC signal generation means of the door phone master is modulated by the downlink audio signal from the door phone master and transmitted to the door phone slave, and the upward audio signal from the door phone slave is transmitted to the door phone master in baseband. Transmitted.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of a television intercom apparatus according to the present invention. In FIG. 1, a door phone master device 101 is connected to a door phone slave device 102 via a communication cable L.
An AC signal generating circuit 103 serving as an AC signal generating means for generating the AC signal f ₀ is connected to one input of a mixer circuit 104 serving as a mixer means. Audio signal f ₂
The microphone 105 for audio input that outputs
Is connected to the other input section of the mixer circuit 104 via the. The output of the mixer circuit 104 is connected to the input of the amplifier 107. The output of the amplifier circuit 107 is connected to the primary side of the transformer 108. Amplifier circuit 107
And the transformer 108 constitute output means. The secondary side of the transformer 108 is connected to the communication cable L. The secondary side of the transformer 108 is connected to a monitor television 111 as display means via a demodulation circuit 109 as a video signal demodulation means for demodulating a video signal and a monitor drive circuit 110. The secondary side of the transformer 108 is connected to the speaker 114 via the bandpass filter 112 and the amplification circuit 113. Note that the microphone 105 and the speaker 114 are integrally provided in a transmitter / receiver (not shown).

On the other hand, the communication cable L is connected to a transformer 115
Is connected to the primary side. The secondary side of the transformer 115 is connected to the input section of the filter 117 via the rectifying diode bridge circuit 116. The diode bridge circuit 116 and the filter 117 constitute DC power supply means. One output portion of the filter 117 is connected to the speaker 119 via the amplifier circuit 118. The other output of the filter 117 is connected to the power supply terminal of the power supply terminal and the amplifier circuit 121 of the TV camera 120 as an imaging means for outputting a video signal f ₁ by photographing a visitor or the like. The output of the television camera 120 is connected to the secondary side of the transformer 115. Also, the audio signal f is supplied to the secondary side of the transformer 115 via the amplifier circuit 121.
A microphone 122 for outputting ₄ is connected.

FIGS. 2 and 3 are a signal waveform diagram and a frequency spectrum diagram for explaining the operation of the embodiment of FIG. 1, respectively. The operation of the embodiment of the TV intercom apparatus of the present invention will be described below with reference to FIGS. First, the microphone 105 and the speaker 11
When the handset consisting of 4 is picked up and hooked up, DC power is supplied to each constituent circuit of the intercom master device 101,
Each component circuit is activated.

The AC output signal f of the AC signal generation circuit 103
₀ is AM-modulated by the audio signal f ₂ input from the microphone 105 via the amplifier circuit 106, and is output to the amplifier circuit 107 as a modulated signal f ₃ . The amplifier circuit 107 amplifies the modulated signal f ₃ and outputs it to the communication cable L via the transformer 108. Modulated signal f3 through communication cable L
Is a diode bridge circuit 1 via a transformer 115
16 is output. The modulated signal f ₃ is double-wave rectified by the diode bridge circuit 116, and the filter circuit 117
Is output to One output signal of the filter circuit 117 is supplied to the power supply terminal of the television camera 120 as a DC power supply. As a result, the television camera 120 enters an operating state. After being rectified by the filter circuit 117, the audio signal f ₂ is output as audio from the speaker 119 via the amplifier circuit 118. When the audio signal f ₂ is not output from the microphone 105, only the AC output signal f ₀ of the AC signal generation circuit 103 is output via the mixer 104, the amplification circuit 107, the transformer 108, and the communication cable L. 102. This signal is converted to a DC power supply as described above, and
Used as a DC power supply.

On the other hand, the audio signal f ₄ output from the microphone 122 is amplified by the amplifying circuit 121, and then the secondary side of the transformer 115, the communication cable L, and the
8, the bandpass filter 112 and the amplifying circuit 113
Is output to the speaker 114 via the. TV camera 1
The video signal f ₁ output by the
Is output to the demodulation circuit 109 via the communication cable L. After the video signal f ₁ is demodulated by the demodulation circuit 109, it is sent to the monitor television 1 via the monitor drive circuit 110.
11 is output. The monitor TV 111, a video display corresponding to the video signal f ₁ is made.

Further, as the transformers 108 and 115,
The type that does not have a center tap for secondary voltage generation on the secondary side is used. In this case, when it is necessary to supply a plurality of types of voltages to the intercom slave 102, DC-
It is necessary to generate various voltages using a DC converter, a bleeder resistor, or the like. However, if a plurality of voltages can be generated by using a plurality of transformers having a center tap for generating a secondary voltage, a DC-DC converter and a bleeder resistor become unnecessary, so that the configuration becomes simple.
Boosting or stepping down can be performed with a small loss.

As described above, according to the present embodiment, the intercom master device 10 is used as a power source for driving the television camera 120.
Since the AC signal f ₀ is supplied from 1, the DC power supply voltage for driving the TV camera 120 does not decrease even when the communication cable L becomes long, and the TV camera 120 can be driven well. Therefore, it is possible to dispose them at various positions without considering the distance between the doorphone master device 101 and the doorphone slave device 102.

Further, since the frequencies of the audio signal from the microphone 105, the audio signal from the microphone 122, and the video signal are different from each other, no interference or the like occurs. further,
Since the output signal of the AC signal generation circuit is used not only as a power source for the intercom slave unit 102 but also for shifting the frequency of the audio signal output from the microphone 105, the frequency shift can be performed with a simple configuration. It is possible to do.

Further, since the transformers 108 and 115 are used, isolation between the intercom master unit 101 and the intercom slave unit 102 is possible, and the effect of countermeasures against lightning also occurs.

[0019]

As is clear from the above description, according to the television door phone apparatus of the present invention, even when the communication cable becomes long, the drive power supply voltage of the door phone handset does not decrease.
Since the TV camera of the intercom slave unit can be driven satisfactorily, it is possible to arrange the intercom master unit and the intercom slave unit at various distances where they could not be arranged conventionally, Not only is the output signal of the signal generation circuit used as the power supply for the intercom slave unit, but also the frequency of the audio signal output from the microphone of the intercom master unit is modulated and used to shift from the audio signal from the intercom slave unit. Since it is possible to perform frequency shift with a simple configuration, interference does not occur.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the present invention.

FIG. 3 is a frequency spectrum diagram for explaining the operation of the present invention.

FIG. 4 is a block diagram showing a conventional TV door phone apparatus.

[Explanation of symbols]

101: Doorphone master unit 102: Doorphone slave unit 103: AC signal generation circuit 104: Mixer 105: Microphone 108: Transformer as output means 109: Video signal demodulation circuit 111 ... monitor television 114 ... speaker 116 ... diode bridge constituting DC power supply means 117 ... filter circuit constituting DC power supply means 119 ... speaker 120 ... television camera 121 as imaging means ... amplifying circuit 122 ... microphone f ₁ ... video signal f ₂ ... audio signal f ₄ ... audio signal L ... communication cable

Claims (1)

(57) [Claims] 1. An AC signal generating circuit (103), a mixer (104) for mixing and modulating an output signal of the AC signal generating circuit with an audio output signal (f ₂ ) of a microphone (105), Output means (108) for outputting a modulated output signal to a communication cable (L); a video signal demodulation circuit (109) for demodulating a video signal (f ₁ ) received via the communication cable; A door phone master unit (101) including a monitor television (111) for displaying an output signal of the mixer as a video signal; DC power supply means for rectifying a modulated signal from the mixer received via the communication cable and generating a DC power supply (116, 117), driven by the DC power supply,
A speaker (119) for outputting a demodulated audio signal from the DC power supply means, an imaging means (120) for transmitting the video signal to the communication cable, and a microphone (122)
And an amplifying circuit (121) for amplifying an audio signal (f ₄ ) output from the communication cable and transmitting the amplified signal to the communication cable at a baseband. Speaker (1) that outputs the baseband audio signal received through the
(14) A television intercom apparatus, comprising: