JPS5847095B2 - Squelch control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a squelch control method used in frequency modulation mobile communication.

There are two types of squelch methods in frequency modulation FM mobile communications.

One is a noise squelch method to eliminate noise that occurs when the receiving device is not receiving a signal, and the other is a tone squelch method to distinguish between groups when the same line is shared by several groups. It is.

Using tone squelch has the advantage that you can talk freely within your own group and not receive calls from other groups, but you must monitor line usage before starting a call.

This monitoring method includes a method of canceling the tone squelch and monitoring the line status, or a method of displaying the line status with a lamp.

However, with the former method, it is necessary to add a switch to the device to cancel the tone squelch, and this type of switch may not be able to be added to some types of communication devices.

In the case of the latter method, it was not possible to monitor the line status sufficiently, and there was a risk of interfering with the communication of the overgroup.

This invention has been made in view of the above points, and provides a method for adjusting the general squelch with a general squelch adjuster and controlling the operation and release of the tone squelch at the same time without adding a special switch. That is.

The figure is a block circuit diagram showing one embodiment of the present invention, in which a part of the transmitting/receiving device is extracted.

In the figure, 1 is a discriminator, 2 is a power amplifier, 3 is a speaker, 4 is a squelch adjuster, 5 is a high-pass filter, 6 is an amplifier, 7 is a detector, and 8 is the output of detector 1. a logically inverting inverter, 9 a squelch adjuster 4;
This noise squelch circuit consists of a high-pass filter 5, an amplifier 6, a detector 1, and an inverter 8, and detects the presence or absence of noise outside the voice band.

10 is a bandpass filter, 11 is a detector, 12 is a bandpass filter 1
13 is a tone squelch circuit consisting of a bandpass filter 10, a detector 11, and a feedback amplifier 12.

14 is a logical product A that operates the power amplifier 2 and drives the speaker 3 only when there are both the output signal of the noise squelch circuit 9 and the output signal of the tone squelch circuit 13.
It is an ND circuit.

That is, when the tone squelch circuit 13 is operating as intended, the power amplifier 2 will not operate unless a specific signal determined by the bandpass filter 10 is received, and therefore the line cannot be monitored.

15 is a differential amplifier that controls the operation of the tone squelch circuit 13, 16 is a switch that causes the tone squelch circuit 13 to oscillate during transmission and maintains the tone signal, 17 is a reception input terminal, and 18 is an output terminal for the tone signal to be modulated for transmission. .

As mentioned above, the basic operation of this squelch circuit is that the speaker 3 operates only when both the noise squelch circuit 9 and the tone squelch circuit 13 output outputs, but when the tone squelch circuit 13 is operating as it should. Since it will not output unless it receives a tone signal of a specific frequency, it will not be possible to monitor the line.

Therefore, an attempt is made to control the tone squelch circuit 13 to enable line monitoring.

That is, the squelch adjuster 4 determines (a) the squelch is open (noise is also emitted from the speaker), (b) only the noise squelch circuit 9 is operating (line monitoring is possible), and (c) the noise squelch circuit 9 and the tone squelch circuit. The differential amplifier 15 is provided to create three types of states in which both the amplifiers 13 and 13 are operating.

When the set value of the squelch regulator 4 is low, the base potential of the transistor Q2 is higher than the base potential of the transistor Q1, the transistor Q1 becomes conductive, and the feedback amplifier 12
make it work.

When the feedback amplifier 12 operates, the oscillation circuit formed between it and the bandpass filter 10 oscillates, and in this state it is in the same state as when it receives a tone signal, the tone squelch is "open", and the power amplifier 2 is operated. Status of Kanji (a)〕
.

Next, when the set value of the squelch adjuster 4 becomes slightly high, the noise squelch circuit 9 starts operating, and the noise output is suppressed.
Moreover, in this state, the tone squelch circuit 13 is still in an oscillating state and line monitoring is possible [state (b) above].

Furthermore, the setting value of the squelch adjuster 4 becomes higher, and the resistance R
When the base potential of the transistor Q□ determined by the voltage division ratio between 0 and the squelch regulator 4 exceeds the base potential of the transistor Q2, the transistor Q2 is cut off and the feedback amplifier 11
The tone squelch circuit 13 stops operating and the tone squelch circuit 13 returns to its original operating state, making it impossible to monitor the line (state (c))].

As mentioned above, the above R) can be achieved by simply adjusting the squelch adjuster 4.
Since it is possible to create three types of states: , (o) and (c), there is no need to control a switch for line monitoring or install a lamp for line monitoring.

In the above embodiment, a differential amplifier is used to control the tone squelch circuit, but the present invention is not limited to this, and various control circuits can be used.

As detailed above, in this invention, when a control signal is applied to the tone squelch circuit, an oscillation circuit is formed and the received audio output circuit is operated regardless of whether or not a tone signal is received, thereby adjusting the human power of the noise squelch circuit. When the set value of the squelch adjuster is below a predetermined value, the tone squelch circuit oscillates to enable line monitoring, and when the set value of the squelch adjuster exceeds the above predetermined value, the tone squelch circuit stops oscillating and resumes its original function. This enables normal transmission and reception operations, and there is no need to provide a special switch to monitor the line.

Further, there is no need to provide a line monitor lamp, and line monitoring can be performed extremely easily.

[Brief explanation of the drawing]

The figure is a block circuit diagram showing the configuration of an embodiment of the present invention. In the figure, 1 is a discriminator, 2 is an audio power amplifier, 3 is a speaker, 4 is a squelch adjuster, 9 is a noise squelch circuit, 10 is a bandpass filter, 12 is a feedback amplifier, 1
3 is a tone squelch circuit, and 15 is a differential amplifier (control circuit).

Claims (1)

[Claims] 1. A noise squelch circuit that detects receiver noise when there is no signal on the receiving input and suppresses the noisy audio output of the received audio output circuit, and has the original function of operating the received audio output circuit only when a predetermined tone signal is received. and a tone squelch circuit configured to configure an oscillation circuit when receiving a predetermined control signal and operate the received audio output circuit regardless of whether or not the tone signal is received, and adjust the input to the noise squelch circuit. and a squelch adjuster that maintains the oscillation of the tone squelch circuit when the set value of the squelch adjuster is below a predetermined value, and stops the oscillation when the set value of the squelch adjuster exceeds the predetermined value, and returns to the original tone squelch. A squelch control system with a control circuit to restore functionality.