JPS6326058A - Sequelch circuit - Google Patents

Abstract

PURPOSE:To improve efficiency of data transmission in semi-duplex communication in an exchange circuit by determining proper squelch time according to the state of link establishment by making echo detection according to the state of link establishment of an exchange circuit, and making it possible to control the state of operation of a receiving section according to the squelch time. CONSTITUTION:A squelch circuit 5 is constituted of an echo detecting circuit 6 that detects echo from received signals and a controlling section 7 that controls operation of a receiving section 3. The echo detecting circuit 6 detects echo of transmitted signals from own station corresponding to the state of link establishment of an exchange circuit and outputs signals for controlling the controlling section 7. The controlling section 7 determines squelch time by output from the echo detecting circuit 6 and control signals from a transmitting section, and further makes control to maintain the receiving section 3 in initial state or to maintain the receiving section in initial state for predetermined squelch time after termination of transmission. Thus, echo detection according to the state of link establishment of the exchange circuit can be performed, and squelch time after completion of transmission until the transmitting section 3 becomes operation state from the initial state becomes proper conforming to the state of link establishment.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a modulation/demodulation device that performs data communication over a voice line, and specifically relates to an improvement of a squelch circuit that controls a receiving section. be.

[Conventional technology]

In systems that use lines to transmit data, a modem is used to send and receive data.When transmitting data, it is modulated and sent to the transmission path, and when receiving data, it is used to modulate the signal sent through the transmission path. I try to retrieve the data by going around twice.

Conventionally, in a system that performs data communication using such a modem, a timer circuit that operates according to a setting signal is used to set the squelch time of the modem, and the control output from this timer circuit The control section controls the operation of the reception section according to the signal and the control signal from the transmission section. This will be explained with reference to FIG.

FIG. 2 is a block diagram showing a conventional squelch circuit.
Conventionally, this type of squelch circuit 1 includes a timer circuit 2 that operates according to several setting signals generated by fixed settings using an option switch, etc., and a control signal from the timer circuit 2 and a transmitter. and a control section 4 that controls the receiving section 3 to maintain an operating state or an initial state using a control signal.

[Problem that the invention seeks to solve]

However, in such a configuration, data transmission is reduced by half.
In terms of data transmission efficiency, half-duplex communication over a switched line is carried out using a method in which information cannot be transmitted in both directions at the same time, but information can be transmitted in both directions by performing switching control. Problems may occur.

That is, the above-mentioned conventional squelch circuit uses a timer circuit 2 that operates according to a fixedly set setting signal, and uses a timer circuit 2 that operates according to a fixedly set setting signal. Since the time required for the receiver to go from the initial state to the operating state is a fixed value, depending on the connection state of the switched line, this may be a limiting factor in improving data transmission efficiency in half-duplex communication. There are drawbacks to this.

It is an object of the present invention to provide a squelch circuit that improves these points and can always perform data transmission efficiently.

[Means for solving problems]

The present invention relates to a squelch circuit that controls a receiving section in data communication, and includes an echo detection circuit that detects an echo from a received signal, and a squelch circuit that controls a receiving section according to a control signal output from the echo detection circuit and a control signal from a transmitting section. The device is characterized by having a control section that controls the operation of the device.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

In FIG. 1, reference numeral 5 denotes a squelch circuit that puts the receiving section 3 into a receiving state, and after the end of transmission, maintains the receiving section 3 in an initial state for a time corresponding to the link establishment state of the switched line, as described later. This squelch circuit 5 differs from the conventional one in that an echo detection circuit 6 detects an echo from a received signal.
Then, the operation of the receiving section 3 is controlled according to the control signal output from the echo detection circuit 6 and the control signal from the transmitting section?
T! It consists of a control section 7 that controls the

That is, in the conventional case, as explained in FIG. 2, there is a timer circuit that operates at a predetermined fixed time period according to a setting signal obtained by selective switch operation by the user, and a timer circuit that operates at a predetermined fixed time period. This configuration has a control section that controls the operation of the receiving section according to a control signal from the transmitting section and a control signal from the transmitting section, but in the case of FIG. 7 has an echo detection circuit 6 that outputs a control signal. This echo detection circuit 6 is connected to a signal line branched from the input side of the receiving section 3, performs echo detection according to the link establishment state of the switched line, and provides its output to the control section 7 as a control signal. .

The control section 7 is supplied with the output of the echo detection circuit 6 as described above, and is also supplied with control signals from the transmitting section, and the state of the receiving section 3 is controlled by these signals.

When the receiving section 3 is controlled by the squelch circuit 5 having such a configuration, the echo detection circuit 6 detects the echo of the transmission signal from the own station device according to the link establishment state of the exchange line, and controls the control section 7. Output the control signal. When the echo detection circuit 6 performs echo detection in this way and its output is given to the control unit 7, the control unit 7 determines the squelch time based on the output from the echo detection circuit 6 and the control signal from the transmitter. And even more control from the transmitter! Control is performed to maintain the receiving section 3 in the receiving state or in the initial state after the end of transmission only during the previously determined squelch time according to the double signal state.

As described above, according to the squelch circuit 5, the echo detection circuit 6 can perform echo detection according to the link establishment state of the switched line, and the echo detection circuit 6 can perform echo detection according to the link establishment state of the switched line. The squelch time is not a fixed value as in the prior art, but is always an appropriate value according to the link establishment state, and the receiving section 3 can be controlled according to such squelch time.

When the squelch time is a fixed value, as mentioned above,
Depending on the connection status of the exchange line, this can cause a drop in data transmission efficiency in half-duplex communication, but with this squelch circuit 5, this does not occur even in half-duplex communication, and data transmission can be carried out efficiently. be exposed.

〔Effect of the invention〕

As explained above, the present invention determines an appropriate squelch time according to the link establishment state by performing echo detection according to the link establishment state of the switched line, and controls the operating state of the receiving section according to the squelch time. By making it possible to do this, it is possible to improve data transmission efficiency in half-duplex communication over switched lines.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the squelch circuit of the present invention, and FIG. 2 is a block diagram of a conventional squelch circuit. 3... Receiving section 5... Squelch circuit 6... Echo detection circuit 7... Control section Fig. 1 Fig. 2

Claims (1)

[Claims] (1) A squelch circuit that controls a receiving section in data communication, which includes an echo detection circuit that detects an echo from a received signal, and a squelch circuit that controls the receiving section according to a control signal output from the echo detection circuit and a control signal from the transmitting section. 1. A squelch circuit comprising: a control section for controlling operation.