JPH0244417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a volume adjustment circuit, and more particularly to a volume adjustment circuit that can perform volume adjustment operations using a test audio signal in a state in which reception radio waves are not detected.

[Conventional technology]

The volume adjustment circuit consists of a mixer, as shown in Figure 1.
An audio signal sent from an IF circuit 3 consisting of a wave detector and the like is input. A volume adjustment circuit 6 constituted by a variable resistor 7 outputs the audio signal inputted to a terminal 6a to a subsequent AF amplifier 8 via a terminal 6b. While monitoring the audio signal output from the speaker 9, the variable resistor 7 is operated to adjust the volume. RF
When the input signal of the frequency corresponding to the tuning circuit set by the module 2 and IF circuit 3 is lower than the desired receiving sensitivity, high level noise is transmitted from the speaker 9 due to abnormal operation of the AGC. A squelch circuit consisting of a squelch noise amplifier 5 and a squelch gate 4 blocks the above noise. Normally, when operating the tuning knob (not shown) to receive broadcast waves, or when scanning an empty channel with a wireless communication device, the squelch circuit changes from open to closed.
Attenuates noise in the main path consisting of the reception circuit at the front stage and the audio circuit at the rear stage. When a desired signal such as a broadcast wave is received, the squelch circuit returns from a closed operation to an open state, and the main path operates normally. The operating conditions of the squelch circuit are determined by the level of the squelch signal, such as the AGC voltage and noise level obtained from the receiving circuit. Squelch volume 5a for wireless communication device
is provided so that the threshold level of the squelch signal can be adjusted. When the squelch volume 5a is operated, the squelch becomes deeper and a weak signal will not open the squelch. If you make the squelch shallower and then turn it off, the squelch circuit will remain open even with a weak signal. In this state, when the variable resistor 7 of the volume adjustment circuit 6 is operated to adjust the terminal 6b toward the ground level, weak signals or noises are attenuated. Rotation toward the terminal 6a, for example clockwise, amplifies the noise associated with a weak signal or no desired radio signal. In addition, in an actual circuit, the squelch 4 is formed by a semiconductor circuit such as a diode or a transistor, or is formed by an IC amplifier or AF provided in the IF circuit 3.
It is muted by a control signal to the field width control pin of the IC amplifier forming the amplifier 8. In either case, when the squelch circuit is closed, the volume cannot be adjusted even if the variable resistor 7 of the volume adjustment circuit 6 is operated.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a volume adjustment circuit that allows effective volume adjustment even when the squelch circuit is closed.

[Means to try to solve the problem]

The present invention includes an oscillator that generates a test audio signal;
The configuration includes test audio signal sending means for sending a test audio signal to the audio adjustment circuit in accordance with the operation of the squelch circuit.

〔Example〕

FIG. 2 is a block diagram of a volume adjustment circuit showing one embodiment of the present invention. This will be explained with reference to FIG.

In FIG. 2, 10 is a test audio signal oscillator. The test audio signal generator 10 oscillates a 1kHz test audio signal. The test audio signal is outputted to the input terminal 6a of the audio adjustment circuit 6 via the switches 11 and 12. The switch 11 is operated and closed by the squelch signal sent from the squelch noise amplifier 5. The variable resistor 13 has a pull-on type key 13b coaxially formed with the slider 13a. When the knob of this slider 13a is rotated, the resistance value of the variable resistor 13 changes, and when the knob is pulled out, the key 13b is closed. Key 13b (hereinafter referred to as
When the user closes the test key), the switch 12 is closed and the test audio signal is output to the input terminal 6a of the volume adjustment circuit 13. The level of the test audio signal at the input terminal 6a of the volume adjustment circuit 6 is adjusted to be the same as the detection output level when the test standard radio wave is input to the preceding receiving circuit. If the reception circuit at the previous stage is out of tune with the desired radio wave, the squelch noise amplifier 5 sends a squelch signal to the squelch gate 4 and switch 11. Therefore, the squelch circuit closes, and noise from the receiving circuit to the terminal 6a of the audio adjustment circuit 6 is blocked, and the speaker 9 becomes silent. switch 1
1 and 12 are AND logic, so even if switch 11 is operated, switch 12 is not closed, so that the test audio signal is not sent to terminal 6a of audio adjustment circuit 6. When a knob (not shown) related to the test key 13b of the variable resistor 13 provided in the audio adjustment circuit 6 is pulled out, the test key 13b is closed and the switch 12 is closed. When the slider 13a of the variable resistor 13 is rotated, the test audio signal is sent to the AF amplifier 8 via the terminal 6b.
A test audio signal corresponding to the rotation of the slider 13a can be monitored by the speaker 9. When the receiving system circuit is tuned to the desired radio wave by the tuning means, the squelch circuit is normally opened. When the squelch circuit is opened, the squelch signal to the squelch gate 4 and the switch 11 is turned off, the main path becomes active, and the switch 11 is restored and turned off. Therefore, the detected desired signal can be monitored by the speaker 9. Since the test audio signal is cut off when the switch 11 is restored, the desired signal and the test audio signal will not be output from the speaker 9 in a superimposed manner. When the desired radio wave is weak, the squelch volume 5a is rotated counterclockwise to make the squelch shallower. When the squelch is made shallow, the point corresponding to the input level of the desired signal that was in the closed area moves to the open area, so the squelch becomes open.

The switches 11 and 12 in the above embodiment may be formed of semiconductor elements. Also, the squelch signal is input to one input side of the AND logic, and the test key 1 is input to the other input side.
3b may be connected, and the starting terminal of the test audio signal oscillator 10 may be activated and oscillated by the logic output. Alternatively, the AND logic output may be connected to one input side of the second AND circuit, and the test audio signal may be applied to the other input side.

〔Effect of the invention〕

The volume adjustment circuit according to the present invention includes an oscillator that generates a test audio signal, and a test audio signal sending means that sends the test audio signal generated by the oscillator to the audio adjustment circuit in accordance with the operation of a squelch circuit. Because of this configuration, the test audio signal to the audio adjustment circuit can be cut off in response to the operation of the test key while the squelch circuit is in operation. Therefore, there is an effect that the volume can be adjusted when there is no signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a wireless communication device related to a conventional volume adjustment circuit, and FIG. 2 is a block diagram of an audio circuit of a wireless communication device showing an embodiment of the present invention. 1... antenna, 2... RF module, 3... IF circuit, 4... squelch gate, 5... squelch noise amplifier, 5a... squelch volume, 6... audio adjustment circuit, 7... speaker, 8... audio signal oscillator for test, 11, 12, 13...Switches.

Claims (1)

[Claims] 1. In a volume adjustment circuit that includes a squelch circuit and an audio adjustment means that adjusts an audio signal that has passed through the squelch circuit, an oscillator that generates a test audio signal, a switch that is controlled by the squelch signal, and a test operation and a test sound to which the oscillator and the circuit of the volume adjustment means are connected when each switch becomes a closed circuit by the switch controlled by the squelch signal and the test operation switch. 1. A sound adjustment circuit, comprising: signal sending means, and configured such that a test sound signal transmitted through the sound adjustment circuit can be monitored by a speaker when the squelch circuit is in a closed operation.