JPS5941348B2 - Video signal distribution and transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal distribution and transmission device, and in particular, it is an object of the present invention to make effective use of wiring and achieve multipurpose functions with a small number of lines.

The present applicant previously filed Japanese Patent Application No. 101811/1984,
When supplying video signals from one parent television receiver to multiple slave television receivers, terminal impedance and buffer amplifiers are inserted in the slave television receivers in use, and In the machine, we proposed a device that would short-circuit these and immediately connect to the subsequent wiring.

By the way, in such a parent-child television set, a video device such as a television camera is provided near the child television receiver, and the video output from this video device is sent to each child television via the parent television receiver. You may want to supply it to a receiver.

For example, if a school is equipped with such a parent-child television device and a child television receiver is placed in each classroom, and the status of one classroom in which this child television receiver is installed is to be broadcast to the entire school. be.

In such cases, conventionally the television camera and the parent television receiver were connected with a dedicated cable, and the output of the television camera was sent to the parent television receiver.

In this method, if the parent television receiver and the slave television receiver are separated, a long cable is required, and it is virtually impossible to move the television camera or the like. The present invention utilizes a cable for transmitting video signals from a parent television receiver to a child television receiver, and sends a video signal from the vicinity of the child television receiver to the parent television receiver, thereby eliminating the need for extra cables. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which a parent television receiver 1 has an antenna 2.
Receives television broadcast radio waves, demodulates them internally, and sends them as video signals to cables 3a, 3b, 3c...
・・3n・・・・Sub-television receiver 4a
, 4b, . . . 4n . . . . Secondary television receivers 4a, 4b...4n...
... has terminal impedance 5a, 5b...
...5n..., buffer amplifiers 6a, 6b.
...6n... and linked switch 7
A, 8a, 7b, 8b,...7n, 8n...
... are connected, and the child television receiver 4a,
When the switches 4b...4n are operating, the switches 7A, 8a, 7b, 8b...7n, 8n are switched as shown in the figure. For example, the cable 3a is terminated by the terminal impedance 5a. Been,
A child television receiver 4a is connected to the secondary television receiver 4a via a buffer amplifier 6a.
and is connected to the subsequent cable 3b. When the secondary television receiver 4a is inoperative, the switches 7A and 8a are in the opposite state as shown in the figure, and the terminal impedance 5a,
The buffer amplifier 6a and the slave television receiver 4a are disconnected from the cable 3a, which is connected directly to the following cable 3b. This prevents negative effects such as reflection and attenuation of video signals caused by connection of the secondary television receivers 4a, 4b, . . . 4n, .

In the figure, reference numeral 9 denotes a television camera installed near the secondary television receiver 4b, and is connected to the cable 3c via a low frequency blocking capacitor 10. The output of the television camera 9 is, for example, a television signal obtained by modulating a carrier wave of about 100 MHz with a video signal.
Since the signals supplied to a, 4b, . . . 4n, . The spectrum in this case is as shown in the second diagram.

In FIG. 2, 11 is the video signal from the parent television receiver in the frequency band below 4.5 MHz, and 12 is the video signal from the parent television receiver in the frequency band below 4.5 MHz.
This is a television signal from a television camera in which a carrier wave of approximately 0.000 MHz is modulated with a video signal. By the way, even if the television signal from the television camera 9 is supplied to the cable 3c in this state, this cable 3c
and the cable 3a connected to the parent television receiver 1, an operating child television receiver, e.g.
If there is a buffer amplifier 6a, the television signal will not be supplied to the cable 3a connected to the parent television receiver 1.

Therefore, in the present invention, these buffer amplifiers 6a
, 6b...6n......, an impedance that is substantially cut off for the frequency band of the video signal and conductive for the frequency band of the television signal. Bypass capacitors 13a, 13b, .
...13n... is inserted.

As a result, the buffer amplifiers 6a, 6b...6n
Even if ... is inserted, the television signal will still be transmitted. The television signal thus transmitted to the cable 3a is supplied via the capacitor 14 to the antenna terminal of the parent television receiver 1, where it is demodulated and each child television receiver 4a, 4b, . . .
...4n... is supplied. In addition, in the illustrated embodiment, the bypass capacitors 13a, 13b...
...13n... is switch 7A, 7b...
It is connected to both ends of ...7n...
Without being limited to this, the buffer amplifiers 6a, 6b...
. . 6n . . . may be placed in parallel with this when inserted into the transmission path.

Also, bypass capacitors 13a, 13b,...
13n, . . . and buffer amplifiers 6a, 6b, .
6n, . . . as shown in the figure, a reactor 15a for blocking the frequency band of the television signal.
, 16a, 15b, 16b,...15n, 16
Even better results can be obtained by inserting n...

In addition, in such a video signal distribution and transmission device, in order to supply the audio signal from the parent television receiver 1 to each child television receiver 4a, 4b...4n... A shielded wire 17 for audio signal transmission is provided, and a video signal generator 18 such as a video tape recorder is connected to the parent television receiver 1. Each child television receiver 4a, 4b,...4n
It is now being supplied to...

This video signal generator 18 is connected to the child television receiver 4.
There are cases where it is desired to perform remote control from around a, 4b, . . . 4n.

In such cases, conventionally it has been necessary to provide a remote control device near the secondary television receiver, for example 4b, and to provide separate wiring for the remote control signal. In this embodiment, such remote control can be performed using the existing shielded wire 17 for audio signal transmission without installing additional wiring, and in FIG. 1, 19 is a remote control device. For example, this device 19 generates a 4-bit pulse as a control signal, and controls the video tape recorder 18 by 10 bits.
00: PLAYlOlOO: STOP, . OO
When the signal is 1O, the control signal is remotely controlled to be in the state of REW, etc. The control signal inside is the control signal receiving circuit 21
and controls the video tape recorder 18.

By the way, this control signal has a pulse waveform as shown in FIG.
Clicking noise occurs in the voice circuit, making it difficult to hear the voice signal.

Therefore, as shown in Figure 3B, ultra-audible frequencies (for example, 40
If a Q carrier wave is used and the carrier wave is transmitted only when a pulse is present, that is, if the carrier wave is amplitude modulated and transmitted, the carrier wave will not be reproduced from the audio circuit and no noise will be generated.

However, even in such a case, if there is a nonlinear portion in the audio signal circuit, the amplitude modulated wave will be envelope-detected and the rising or falling portion of the pulse will appear as click noise. Therefore, as shown in FIG. 3C, if the carrier wave is frequency modulated and the carrier wave frequency is raised (or lowered) only while the pulse is present, no noise will appear in the audio circuit. This may be demodulated by the control signal receiving circuit 21 to control the video tape recorder.

Since the present invention has the above-mentioned configuration, it has the advantage of being able to perform multipurpose functions with a small number of existing wiring lines and increasing the utility value of the video signal distribution and transmission apparatus.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIGS. 2 and 3 are graphs used for explaining the same. 1... Parent television receiver, 2...
Antenna, 3a, 3b, 3c,...3n...
...Cable, 4a, 4b, ...4n...
...Sub television receiver, 5a, 5b...
5n...Terminal impedance, 6a, 6
b...6n...Buffer amplifier, 7a
,7b...7n...,8a,8b...
...8n... Switch, 9... Television camera, 10, 13a, 13b...
13n..., 14, 20... Capacitor, 15a, 15b,... 15n...
, 16a, 16b...16n...Reactor, 17...Shield wire for audio signal transmission, 1
8...Zedeo tape recorder, 19...
Remote control device, 21... Control signal receiving circuit.

Claims (1)

[Claims] 1 A plurality of child television receivers, a parent television receiver for supplying video signals to the child television receivers, and a parent television receiver for supplying video signals from the parent television receiver to the child television receivers. A television that transmits a video signal transmission line that includes a buffer amplifier in its circuit, and that is provided near the child television receiver and supplies the video signal transmission line with a television signal of a higher frequency band than the video signal. a video device such as a camera, and a bypass circuit provided in parallel with the buffer amplifier in the transmission line, which substantially cuts off the video signal and substantially conducts the television signal; A video signal distribution and transmission device comprising means for supplying a television signal in a transmission line to an antenna terminal of the parent television receiver.