JPS59856Y2 - CATV transmission equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a CATV transmission device, and is particularly suitable for automatic meter reading of electricity, gas, water, etc. late at night when no television broadcasts are being conducted.

Generally, in a CATV system, signals from the head end are not only sent to the terminal, but also sent in the reverse direction from the terminal to the head end for purposes such as utility meter reading, independent broadcasting, disaster prevention, and various response confirmations. .

For this reason, conventionally it was necessary to use two cables, and in the case of one cable, it was necessary to use a bidirectional amplifier.

This bidirectional amplifier is an amplifier used in the middle of one cable, and has two amplifying sections (a down amplifying section and an up amplifying section) in opposite directions with different frequency bands, so it is expensive, and it also requires two cables. The product used also had the disadvantage of being expensive.

The present invention eliminates the above-mentioned drawbacks by providing a control signal detection circuit and a switch circuit in an amplifier used in the middle of one cable, and when the control signal from the head end disappears, the switch circuit detects the control signal. The purpose of the present invention is to provide an inexpensive CATV transmission device in which the amplifying section of the amplifier is switched from the down amplifying section to the up amplifying section by operating the .

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a CATV system, which is comprised of a well-known headend 1 and a plurality of trunk amplifiers 2.3.4.5 for amplifying television signals from the headend.

The television signal from the head end 1 is transmitted to the amplifier 2,
3, 4. Terminal via 5 (this direction is referred to as downstream)
is supplied to

These amplifiers 2, 3, and 4.5 each have an input terminal 6, an output terminal 7, an amplification section 8, and an input side of the amplification section connected to the input terminal 6 or output terminal 7, as shown in FIG. A switch circuit 9 that selectively connects, a switch circuit 10 that selectively connects the output side of the amplification section 8 to the output terminal 7 or the input terminal 6, and a control section that switches and drives these switch circuits 9 and 10. 11, a circuit 12 that detects a control signal for issuing a command for the control section, and a coupling section 13 that supplies signals from the input terminal 6 to the circuit and the switch circuits 9 and 10. .

Further, a generator (not shown) for generating the control signal is installed on the head end 1 side.

In the CATV transmission device described above, the control signal from the generator is set at a frequency that is within the downlink television signal band (within the transmission band of the amplifiers 2, 3, 4, and 5), and is set at a frequency different from that of the television signal. There is.

This control signal is transmitted together with the television signal during television broadcasting.

Therefore, in the amplifier 2, the television signal and the control signal from the input terminal 6 are inputted to the coupling section 13, and the control signal detected by the detection circuit 12 from the coupling section is transmitted to the control section 13.
1, and based on the command, the control section 11 drives the switch circuits 9 and 10 so as to switch them to the solid line side shown in the figure.

On the other hand, the television signal and control signal from the coupling section 13 are switched to the solid line side of the switch circuit 9 and the amplifier section 8.
and the above switch circuit 1 switched to the solid line side above.
0 to the output terminal 7 and is supplied to the amplifier 3.

Amplifier 3 acts similarly to amplifier 2, and television signals and control signals pass through amplifiers 4 and 5 in the same manner.

After the television broadcast ends, the control signal is no longer detected by the detection circuit 12 by stopping the generation of the control signal, and as a result, the control section 11 issues a command to the switch circuit 9. , 10 are driven so as to switch to the dashed line side.

When the switch circuits 9 and 10 are switched to the dashed line side, the input terminal of the amplifier section 8 is connected to the output terminal 7, and the output side is connected to the input terminal 6, so that the amplifiers 2 and 3°4.5 are connected to the upstream side. Due to the amplification connection, signals cannot be transmitted from the head end 1 to the terminal, but various types of TV can be transmitted from the terminal to the head end 1 at frequencies within the same band as the television signal.

It should be noted that the present invention can also be implemented by detecting that the control signal has reached a level below a specified value and switching the switch circuits 9 and 10 to the dashed line side.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a block diagram and FIG. 2 being a block diagram of the main parts. 1... Head end, 2, 3, 4.5...
...Main line amplifier, 8...Amplification section, 9, 10...
...Switch circuit, 12...Circuit for detecting a control signal.

Claims (1)

[Scope of utility model registration request] A circuit provided in each main line amplifier of the CATV system to detect a control signal of a frequency different from the TV signal within the downlink TV signal band, and a circuit provided in each of the above main line amplifiers to detect a control signal that is within the downstream TV signal band and has a frequency different from that of the TV signal. a switch circuit that switches the direction of the amplification section by inverting the connections to the input/output terminals of the amplification section, and a generator that generates the control signal provided on the head end side of the CATV system, Sometimes the control signal is transmitted together with the TV signal, and after the TV broadcast ends, the transmission of the control signal is also stopped and the transmission direction of the CATV system is reversed, so that each subscriber's terminal transmits the control signal within the same band as the TV signal. CAT is characterized by transmitting various data to the headend side at the frequency of
V transmission device.