JPH0358535A - Signal transmission equipment - Google Patents

Abstract

PURPOSE:To easily and surely send a desired signal in bidirection by separating a signal transmitted based on a voltage across a terminating resistor from a transmission signal. CONSTITUTION:A 2nd transmission signal SV is separated from a 1st transmission signal SSYNC based on the voltage of a 1st terminating resistor 8 at the side of a 1st signal output circuit 46 and the side of a transmission line 10, 2ESYNC+EDC1 and EV+ESYNC+EDC. Moreover, a 1st transmission signal SSYNC is separated from a 2nd transmission signal SV based on the voltage of a 2nd terminating resistor 14 at the side of a 2nd signal output circuit 52 and the side of the transmission line 10, 2EV and EV+ESYNC. Thus, the 1st and 2nd transmission signals SSYNC and SV are transmitted in bidiretion via the transmission line 10 simply and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a signal transmission device, and is suitable for application to, for example, a surveillance television camera that operates in synchronization with an external synchronization signal. ? Summary of the Invention The present invention provides a method for easily and reliably transmitting a desired signal in both directions in a signal transmission device by separating a transmitted signal from a transmitted signal based on the voltage across a terminating resistor. I can do it.

C. Prior Art Conventionally, surveillance television cameras have been designed to operate in synchronization with a synchronization signal output from, for example, a central surveillance device.

For this reason, when installing this type of surveillance television camera, a transmission path for synchronizing signal transmission is provided in addition to a transmission path for video signals. D Problems to be solved by the invention By the way, in such a surveillance television camera, if a synchronization signal can also be transmitted on the transmission line for video signal transmission, the number of transmission lines to be laid can be reduced accordingly. It is considered to be advantageous and convenient. In this case, for example, a method can be considered in which the synchronization signal is modulated and transmitted, as shown in Figure 2. That is, on the monitoring device side l, the modulation circuit 2 is configured to gate the dynamic transmission signal S03 of a predetermined frequency (for example, four times the subcarrier frequency) based on the synchronization signal ssv}Ic, and thereby the carrier signal S. ，，
is modulated by the synchronization signal S3yNc, and the modulated signal S. 4.

. through a bandpass filter circuit (BPF) 3
to circuit 4.

The power supply circuit 4 supplies a modulation signal Sl400 to a predetermined drive power supply.
After being superimposed, the signal is outputted to a transmission line 10 made of a coaxial cable via a terminating resistor 8 (Japanese Utility Model Publication No. 51-30585).

On the other hand, on the television camera side 2 side, the video signal Sv is outputted to the transmission line 10 via the terminating resistor 14, and as a result, on the monitoring device side 1 side,
Buffer circuit 16 and low-pass filter circuit (LPF)
The video signal Sv can be received by extracting low frequency signal components from the output No. 3 of the transmission line 10 via the output A3 of the transmission path 10 in sequence.

Furthermore, on the television camera 12 side, the modulated signal S. . (Japanese Utility Model Publication No. 54-4893), the modulated signal S MOD is passed through an automatic gain control circuit (
AGC) 22 captures the signal to a predetermined signal level. Further, a demodulation circuit 24 generates a modulated signal S. After demodulating 0, the synchronizing signal S is shaped by waveform shaping through the waveform shaping circuit 26.
3YNC can be reproduced.

By transmitting the video signal based on the synchronization signal s3YNl: reproduced in this way, it is considered that the video signal and the synchronization signal can be transmitted bidirectionally using one transmission path 10, and 2 can be obtained.

However, in this method, the synchronizing signal must be modulated and demodulated and the bands must be separated, making the overall structure complicated.

In contrast, the monitoring device adds and outputs a direct synchronization signal,
A method of separating the synchronization signal and video signal from the combined waveform using a clamp circuit or the like may be considered, but in this method, there is a problem that it becomes difficult to separate the synchronization signal and video signal reliably and stably. ．． The present invention has been made in consideration of the above points, and attempts to propose a simple signal transmission device that can transmit video signals and synchronization signals in both directions using a single transmission path. It is something. E Means for Solving the Problem In order to solve this problem, in the present invention, first and second terminating resistors 8 and 14, which terminate both ends of the transmission line 10 and the transmission line IO, respectively, are provided. A first signal output circuit 46 that outputs the first transmission signal S11'/NC to the second terminating resistor l4 side via the terminating resistor 8 and the transmission line 10; Via the transmission line 10,
The second signal output circuit 52 outputs the second transmission signal Sv to the first terminating resistor 8 side, and the voltage 2EsvN on the first signal output circuit 46 side and the transmission line 10 side of the first terminating resistor 8
Based on c+El,cl and Ev+E,yNc+Eoc, the second transmission signal Sv is converted to the first transmission signal ssv
The first signal separation circuit 71 separated from the Nc and the second terminating resistor 14 on the second signal output circuit 52 side and the transmission line 1
Based on the voltage 2E on the 0 side and Ev +EstNc,
A second signal separation circuit 86 is provided to separate the first transmission signal S3YNC from the second transmission signal Sv. Voltage 2 on the first signal output circuit 46 side and the transmission line 10 side of the F action first terminating resistor 8 EsvNc+Eoe+ and Ev
+EsyNc+Eoc, the second transmission signal Sv
from the first transmission signal S S'lHC, and
If the first transmission signal SSVNC is separated from the second transmission signal Sv based on the voltages 2Ev and Ev+EsvNc on the second signal output circuit 52 side and the transmission line 10 side of the second termination resistor l4, One transmission line 1 easily and reliably
0 in both directions via the first and second transmission signals S, respectively.
svNc and Sv can be transmitted. G. Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, 40 indicates a signal transmission device as a whole, and between a television camera side 42 and a monitoring device side 44,
A synchronizing signal S svNc and a video signal Sv. Transmit. That is, on the monitoring device side 44, the power supply circuit 46 receives the driving power supply v! The synchronization signal S is stabilized at a predetermined power supply voltage.
*After superimposing VNC, the transmission line l is connected via the terminating resistor 8.
Output to O. Incidentally, the terminating resistors 8 and l4 are selected to match the characteristic impedance of the transmission line 10.

On the other hand, on the television camera side 42, the transmission line 10 is terminated with a terminating resistor 14 via a coupling capacitor 48, so that the transmission line 10
0 is separated from other signals and taken into the power supply circuit 50. The power supply circuit 50 stabilizes the drive power taken in and then supplies it to a television camera (not shown), whereby the power supplied from the monitoring device 44 via the transmission path 10 is used to power the television camera. can be driven.

On the other hand, after amplifying the video signal SV output from the television camera, the amplifier circuit 52 amplifies the terminating resistor 14,
It is output to the transmission line 10 via a coupling capacitor 4.

As a result, on the monitoring device 44 side, the video signal Sv and the synchronization signal svsc are held at the signal levels Ev and E@vNc on the transmission line 10 side on the terminating resistor side. At this time, the video signal Sv is held at the O level on the power supply circuit 46 side of the termination resistor 8, and the synchronization signal Ssync is held at the signal level 2E1ymc, which is twice that on the input end side. Incidentally, on the transmission line 10 side and the power supply circuit 46 side of the terminating resistor 8, the voltage of the drive power supplied from the 1i source circuit 46 is set to EIIC and E, respectively.
Represented by DcI. Therefore, on the transmission line 10 side of the terminating resistor 8,
The terminal voltage can be expressed as Ev + Esvne + Eoc, whereas on the power supply circuit 46 side, the terminal voltage is 2E■.

10E. c. It can be expressed as The operational amplifier circuit 62 has a feedback resistor 64 having a resistance value R, an input resistor 66 at an inverting input terminal, an input resistor 68 at a non-inverting input terminal, and an input resistor 68 at a non-inverting input terminal set to resistance values 2R and 2R, respectively. A differential amplifier circuit 71 is configured together with the grounding resistor 70 of the input resistors 66 and 6.
The input signal of 8 is amplified at a ratio of 1/2:1 and fIJi is calculated. In contrast, input resistors 66 and 68 are connected to both ends of terminating resistor 8 via coupling capacitors 72 and 74. Therefore, in the terminal voltage of the terminating resistor 8, the terminal voltage Ev 1 E svNc on the transmission line IO side and the power supply circuit 46 side
+E oc and a portion of the direct current of 2 EsvNc+Esc+ is removed, resulting in a voltage E y + E svHc and 2Es
VNc is input to the input resistors 66 and 68, and as a result, an output signal having a signal level Ev expressed by the following equation 1 can be obtained via the operational amplifier circuit 62. In this way, by separating the transmitted video signal Sv from the transmitted synchronizing signal SAYE C based on the terminal voltage across the terminal resistor 8, a simple i-precept of just subtracting in the differential amplifier circuit 7l can provide reliable results. It is possible to separate the video signal S▼ into two. Similarly, on the television camera side 42, the operational amplifier circuit 77 has an input resistor 81 at the inverting input end set to resistance values 2R, R and 2R, respectively, and a non-inverting input end with respect to the feedback resistor 79 having a resistance of only R. A differential amplifier circuit 86 is configured together with the input resistor 83 and the ground resistor 85 at the non-inverting input terminal, and thereby the human input signals of the human input resistors 83 and 85 are amplified and subtracted at a ratio of 1/2:1. It is done like this.

At this time, at the terminal voltage of the terminating resistor 14, the transmission line l
While the O side can be expressed as Ev +EsvNc, the amplifier circuit 52 side can be expressed as 2Ev.
7, the following formula l (Ev + Esysc) (2 Ev
) 1E! An output signal with a signal level B S'lHC expressed as vNc2 (2) can be obtained.

Thus, based on the terminal voltage across the terminal resistor 14, the synchronization signal SSYH transmitted from the video signal Sv to be transmitted
By separating the synchronization signal S, the synchronization signal S can be reliably obtained with a simple configuration that only requires the differential amplifier circuit 71 to perform subtraction processing. H, can be separated.

Therefore, the video signal Sv and the synchronization signal svNc can be transmitted bidirectionally using one transmission line 10 with a simple structure as a whole.

Thus in this example? f'JR circuit 46 is
A first terminating resistor 8 that terminates the transmission line 10 and the transmission line 10
A synchronizing signal S3YNC is applied to the second terminating resistor 14 through
The amplifier circuit 52 outputs the video signal Sv to the first terminating resistor 8 side via the second terminating resistor 14 and the transmission line 10. A second signal output circuit is constructed.

On the other hand, the differential amplifier circuit 71 has a voltage 2 of the first terminal resistor 8 on the first signal output circuit 46 side and the transmission line 10 example.
E SYNC + E! IcI and Ev +Esv
Based on Nc+Eoc, the video signal S, which is the second transmission signal, is converted to the synchronization signal S, which is the first transmission signal.
In contrast, the first signal separation circuit separates the signal from the first signal separation circuit.
The differential amplifier circuit 86 is configured to maintain voltages 2Ev and E of the second terminal resistor 14 on the second signal output circuit 52 side and the transmission line 10.
Based on v + E svNc, synchronization signal S sv
A second signal separation circuit is configured to separate Nc from the video signal Sv.

In the above configuration, the synchronizing signal S SVHC is transmitted to the television camera side 42 together with the drive power source via the termination resistor 8 and the transmission line IO, and is maintained at the signal level of ES'fNC on the transmission line IO side of the termination resistor 14. On the other hand, it falls to the 0 level on the amplifier circuit 52 side of the termination resistor 14.

On the other hand, the video signal Sv is transmitted through the terminating resistor 14 and the transmission line 1.
0 to the monitoring device side 44, and at this time, it is held at a signal level of 2Ev on the amplifier circuit 52 side of the terminating resistor 14, whereas it is held at a signal level of Ev on the transmission path side of the terminating resistor 14. .

Therefore, each terminal voltage of the terminating resistor l4 is E3YNc+Ev
and 2E, and the corresponding terminal voltage is applied to the differential amplifier circuit 8.
The transmitted synchronizing signal S3YNC is separated from the transmitted video signal Sv by being amplified by 6 and subtracted at a ratio of 171/2.

Similarly, in the terminating resistor 8, the terminal voltage of the ita circuit 46 is 2 E sv. c + E oc+, transmission line 1
After the terminal voltage on the 0 side is held at Ev + EsvNc + Eoc and the DC voltage of the terminal voltage is removed, the synchronization signal S to be transmitted is amplified and subtracted at a ratio of 1/2:1 by the differential amplifier circuit 71. ! The video signal Sv transmitted from YNC is separated.

According to the above configuration, the synchronization signal S SYNC to be transmitted is determined based on the terminal voltages across the terminal resistors 8 and 14, respectively.
Alternatively, by separating the video signal Sv or the synchronization signal SSVNc transmitted from the video signal Sv, the video signal Sv and the synchronization signal SSVHC can be reliably obtained with a simple configuration that only performs subtraction processing in the differential amplifier circuits 71 and 86. Thus, it is possible to obtain a signal transmission device 40 with a simple configuration that can bidirectionally transmit the video signal Sv and the synchronization signal svNc using one transmission path 10.

In the above-described embodiments, a case has been described in which a synchronization signal is transmitted from the surveillance equipment side, but the present invention is not limited to this. For example, in addition to a synchronization signal, a control signal for remotely controlling a television camera is transmitted. You can also do this.

Further, in the above-described embodiment, a case has been described in which the video signal and the synchronization signal are transmitted bidirectionally, but the signals to be transmitted are not limited to this, and various signals can be transmitted as necessary.

1I Effects of the Invention As described above, according to the present invention, by separating the transmitted signal and the transmitted signal based on the terminal voltages at both ends of the terminating resistor, the signal can be reliably transmitted with a simple structure. In this way, it is possible to obtain a simple elliptic signal transmission device that can transmit signals in both directions using one transmission path.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a signal transmission device according to an embodiment of the present invention, and FIG. 2 is a block diagram for explaining the "=%=e problem. 8, 1 4... Termination Resistor, lO...Transmission line, 7 1, 86...Differential amplifier circuit. Proxy Keiki Tanabe

Claims (1)

[Scope of Claims] A transmission line; first and second terminating resistors terminating both ends of the transmission line, respectively;
a first signal output circuit that outputs a first transmission signal to the terminating resistor side of the terminating resistor;
a second signal output circuit that outputs a second transmission signal to the terminating resistor side; and a second signal output circuit that outputs a second transmission signal to the terminating resistor side; a first signal separation circuit that separates the transmission signal from the first transmission signal; and a first signal separation circuit that separates the transmission signal from the first transmission signal; and and a second signal separation circuit that separates the first transmission signal from the second transmission signal.