JPS5941936A - Monitor system by voice squelch - Google Patents

Abstract

PURPOSE:To prevent the service impossibility due to forgetting of power-on, by providing an LPF, through which main band components of an voice signal pass, and a switch circuit, which is operated by the output of this LPF, in the output of a receiver, and making a monitor amplifier operated when the voice signal is inputted. CONSTITUTION:The receiving signal output from a receiver 1 is branched to three directions by a branching circuit 2 and is inputted to a demodulating circuit, monitor amplifier 7, and an LPF3. In this LPF3, the signal frequency for data communication is cut off, and only main frequency band components of the voice signal are permitted to pass through; and the output of LPF3 is applied to a squelch amplifier 4. A squelch level is set by this amplifier 4, and output ''1'' or ''0'' is supplied to a delay circuit 6 in accordance with the level of the input voice signal, and analog switches 11 and 12 connected to the amplifier 7 are controlled by output signal (d) of the circuit 6. The amplifier 7 is made operated when the voice signal is inputted, thus preventing the occurrence of the service impossible state due to forgetting of power-on.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an audio monitoring system for a receiver, and more particularly to an audio squelch monitoring system in which a monitor amplifier is automatically activated only when audio is received.

PRIOR ART AND PROBLEMS A voice receiver circuit is widely used because it directly monitors the presence or absence of communication and the content of communication by voice in a line for communicating by voice. Conventionally, for such a receiver monitor circuit, a method was generally used in which the monitor amplifier was manually powered on.

On the other hand, a wireless communication system has been developed and put into practical use that uses the same wireless line to perform data communication using signals in radio wave format F2 and voice calls using signals in radio wave format F3. In these two lines, during normal operation, only audible signals for data communication are transmitted, so there is no need for monitoring, and therefore the monitor device is often turned off. On the other hand, when making a voice call for the purpose of maintenance, for example, it is necessary to turn on the power to the monitor device in advance, and if you forget to turn on the power, the call will be disabled and you will have to make a call. A situation arises in which it is impossible to do so.

OBJECTS OF THE INVENTION The present invention attempts to solve the problems of the prior art, and its purpose is to add a voice squelch circuit that operates only by voice signals to a receiver monitor circuit, and to receive a call tone. The object of the present invention is to provide a system that automatically turns on the power to a monitor amplifier when the monitor amplifier is turned on, thereby preventing the occurrence of a call failure state due to forgetting to turn on the power, as in the case of the C1 manual system.

Structure of the Invention The voice squelch-based monitoring system of the present invention is useful for data communications in wireless communication systems, etc. that share the same wireless line and perform data communication using signals in radio wave format F2 and voice calls using signals in radio wave format F5. By making the signal frequency of audible sound and the main frequency components of a voice call different in frequency band, and dividing the transmission band into high and low frequencies.
Focusing on the fact that the receiver output signal can be separated by passing it through a low-pass filter, we added only the muffled audio signal to the audio squelch circuit, and used the squelch circuit's detection signal to turn on the monitor amplifier power. This is what I did.

Embodiment of the Invention FIG. M1 shows the configuration of an embodiment of a monitoring system using voice squelch according to the present invention. In the figure, 1 is the receiver, 2
is a branch circuit, 6 is a low-pass filter, 4 is a squelch amplifier, 5 is a semi-fixed resistor for squelch level adjustment, 6 is a return delay circuit, 7 is a monitor amplifier, 8 is a volume adjustment resistor, 9 is a semi-fixed resistor for volume adjustment, 10 is a volume adjustment circuit changeover switch, 11.12 is an analog switch, 13 is a power switch, and 14 is a monitor speaker.

In addition, Fig. 2 shows the signals of each part in the circuit of Fig. 1, and α
is the received signal output and indicates the input of the low-pass filter 3, b is the output signal of the low-pass filter B, σ is the output signal of the squelch amplifier 4, d is the output signal of the recovery delay circuit 6, and each of these signals is They are also indicated in FIG. 1 by the same reference numerals.

At 1 in FIG. 1, a received signal output from a receiver 1 is applied to a branch circuit 2, where it is branched in three directions, and input into a demodulation circuit, a monitor amplifier, and a low-pass filter 3. The input signal to the low-pass filter 6 consists of either an audible sound signal A for data communication or a voice B for telephone calls, as shown in FIG. 2 α. The cutoff frequency of the low-pass filter 3 is selected so as to cut off the data communication signal frequency but pass the main frequency band components of the audio signal. Therefore, as shown in Figure KS2, only the audio signal is transmitted. After passing through the low-pass filter 3, the squelch amplifier 4
added to. The squelch level of the squelch amplifier 4 is set by a semi-fixed resistor 5 for adjusting the squelch level, and the output changes between "1" and "1" depending on whether the input signal level exceeds the squelch level. becomes. FIG. 2C shows the output of the squelch amplifier 4 corresponding to the audio signal shown in FIG. The delay circuit 6 has an input (ri level is “1”)
Even if it changes from the state to On, it maintains the 1" state within a certain period of time.Therefore, if a signal like the one shown in □ is input, the short-time 0'' are canceled to produce a continuous output as shown in FIG. 2d. The output of the return delay circuit 6 is applied to an analog switch 11.12.

When the analog switches 11 and 12 receive a "1" level input to the signal terminal S, the analog switches 11 and 12 establish conduction between the input terminal IN and the data terminal. Therefore, when the analog switch 12 becomes conductive in response to "1" in the signal d, the power supply V is applied to the monitor amplifier 7, and when the analog switch 11 becomes conductive, the sound Ji:i! A semi-fixed resistor 9 for adjustment is connected between the monitor amplifier 7 and ground via a volume adjustment circuit changeover switch 10. As a result, the monitor amplifier 7 generates an audio output at the level set by the volume adjustment semi-fixed resistor 9 in response to the input provided via the branch circuit 2, and this audio output is emitted via the speaker 14. , audio monitoring can be performed.

The return delay circuit 6 is provided to prevent the monitor amplifier from being powered off every time the audio signal is interrupted for a short time, thereby making the monitor sound easier to hear. The return delay time of the return delay circuit 6 is determined depending on the call situation and the like, and is set to about 3 seconds, for example.

When performing manual operation in the circuit shown in FIG. 1, the associated switches 10 and 13 are turned on.

As a result, the power supply V is applied to the monitor amplifier 7 via the power switch 13, and the volume adjustment resistor 8 is connected between the monitor amplifier 7 and the ground via the sound ml-adjustment circuit changeover switch 10. It operates at the level determined by the volume adjustment resistor 8. sound, J
? 1. The adjustment resistor t3 is a variable resistor, and is designed to arbitrarily adjust the volume of the monitor sound.

As described in detail, according to the voice squelch monitoring system of the present invention, a low-pass filter that passes only the main band components of the voice signal is provided at the output of the receiver, and a squelch circuit that is operated by the output of the low-pass filter is provided. Since the monitor amplifier is automatically put into operation when an audio signal is input, it is possible to prevent the situation where a call cannot be made due to forgetting to turn on the power, which is the case with manual systems.
Extremely effective.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the voice squelch monitoring system of the present invention, and FIG. 2 is a time chart showing various signals in the circuit of FIG. 1. DESCRIPTION OF SYMBOLS 1...Receiver, 2...Branch circuit, 3...Low pass filter, 4...Skelp amplifier, 5...Semi-fixed resistor for level adjustment, 6...Return delay circuit, 7... ...Monitor amplifier, 8.Volume adjustment resistor, 9.Semi-fixed resistor for soundscape adjustment, 10.Volume adjustment circuit selection switch,
11.12... Ana e+ switch, 13... Power switch, 14... Monitor speaker Patent applicant Fujitsu Limited representative patent attorney Gobe Tamamushi (3 others)

Claims (1)

[Claims] In a receiver output monitor circuit for a line in which the same line is shared by an audio signal and an audible signal having a frequency range p higher than the main band of the audio signal, the main band of the audio signal is passed and the audible audio signal is blocked. and a squelch circuit that operates to generate an output when the output of the low-pass filter is above a certain level, and a receiver output monitor circuit is activated in response to the output of the squelch circuit. Monitoring method using voice squelch.