JPH03248629A - Fm communication equipment - Google Patents

Abstract

PURPOSE:To easily eliminate a squelch tail period by putting off a power after lapse of an operation delay time of a tone squelch detection function after a tone is lost at the end of talking. CONSTITUTION:As soon as a PTT(press-to-talk) switch is closed similarly to a conventional system at talking from a transmitter side, tone and power are transmitted. The transmission of a tone is deenergized when the PTT is opened at the end of talking and the transmission of power is deenergized after lapse of the operation delay time (t) of the tone squelch detection function of the receiver. Thus the circuit sending a signal while the phase and frequency of the tone are varied to eliminate the squelch tail period is not required for the transmitter and the circuit detecting a change in the tone is not required for the receiver. Moreover, a time after the output of tone and the PTT are opened till the transmission of power is tuned off has only to be the operation delay time (t) of the tone squelch detection function of the opposite receiver or over, a time of 180msec is in general enough.

Description

[Detailed description of the invention] and industrial application fields. The present invention relates to an FM communication device.

More specifically, the present invention relates to an FM communication device with a tone squelch function that easily removes squelch tails.

[Prior art] Conventionally, in FM communication equipment, when one radio wave is shared by multiple lines, a specific station is selected to configure the communication line, so the transmitter side has to transmit audio at frequencies below 250 Hz. A tone squelch function is used in which a certain tone is superimposed and transmitted, and the receiver side connects the audio amplification unit or speaker only when a tone matching the own station arrives.

In this communication device, when a tone is simply superimposed on the voice, that is, when the breath talk switch (PTT) is turned off at the end of a call on the transmitter side, the tone and high frequency transmission output (power) are also turned off at the same time. In this case, the receiver demodulates the noise during the period from when the tone is no longer received until the tone squelch detection function operates and disconnects the audio amplification unit or speaker (the operation delay time of the tone squelch detection function). As a result, you will momentarily hear a buzzing sound or squelch tail, and the quality of the call will deteriorate.

For this reason, conventionally, the transmitter side has been using PTT at the end of a call.
Even after turning OFF, a tone is sent out by changing the frequency and phase for a certain period of time, and the receiver side detects the change in tone and disconnects the audio amplification section or speaker, thereby suppressing the squelch tail. A communication method has been adopted to remove this.

FIG. 2 is a time chart of PTT, tone, and power on the transmitter side of an FM communication device that employs such a communication method.

As shown in the figure, on the transmitter side of this communication device, PTT is turned on during a call, tone and power transmission is also turned on when transmitting voice, and PTT is turned off at the end of the call.
Then, the frequency and phase of the tone change for a certain period of time (the shaded area in the figure), and then the transmission of the tone and power is turned off.

[Problems to be Solved by the Invention] Since the conventional FM communication device with a tone squelch function as described above is configured as described above, in order to remove the squelch tail, the transmitter side changes the frequency and phase of the tone. In addition, a circuit for detecting changes in tone frequency and phase is also required on the receiver side, but such circuits are complicated and expensive.

In addition, squelch tail removal cannot be performed effectively unless both the transmitter and receiver sides use the same communication method for not only the tone squelch function but also squelch tail removal. There were also problems.

The present invention has been made to solve this problem, and an object of the present invention is to provide an FM communication device with a tone squelch function that can easily remove squelch tails.

[Means for Solving the Problems] An FM communication device according to the present invention is an FM communication device with a tone squelch function, in which the transmission of a tone from a transmitter is stopped at the end of a call, and the operation delay time of the tone squelch detection function of a receiver is reduced. Later, it was decided to stop the transmission high-frequency output (power).

[Operation] In this invention, when the transmitter side turns off the PTT at the end of a call, the transmission of the tone is also turned off, but the power is not turned off together with the PTT and the tone, and the operation of the tone squelch detection function of the receiver is delayed. It is in the sending state during this time. Therefore, on the receiver side, during the operation delay time of the tone squelch detection function, the power white noise is demodulated and there is no sound. Then, the tone squelch detection function of the receiver operates, and after the audio amplifying section or the speaker is cut off, the power transmission from the transmitter side is turned off. This eliminates the need to demodulate noise on the receiver side, eliminating the squelch tail.

[Example] An example of the present invention will be described below with reference to the drawings. FIG. 1 shows the PTT on the transmitter side of the FM communication device according to the present invention.
, a time chart of tone and power. As shown in the figure, during a call, the transmitter side of the present invention turns on the PTT and transmits tone and power at the same time as in the conventional system, but when the call ends, the PTT is turned off.
When this happens, the tone transmission is set to 0FFL, and the power transmission is turned off after the operation delay time (1) of the tone squelch detection function of the receiver has elapsed.

Therefore, in order to eliminate the squelch tail, the transmitter does not need a circuit that changes the phase or frequency of the tone and sends it out, and the receiver also does not need a circuit that detects such tone changes.

The time from turning off PTT and tone output to turning off power transmission should be at least the operation delay time (1) of the tone squelch detection function of the other party's receiver, and should generally be 180m5ec. I can do it. This time can be easily set using the transmitter's program.

[Effects of the Invention] As described above, the present invention makes it possible to easily remove the squelch tail by turning off the tone at the end of a call and then turning off the power after the operation delay time of the tone squelch detection function of the receiver has elapsed. I can do it. Therefore, there is no need to provide a complicated circuit for removing squelch tails in the transmitter and receiver, and squelch tails can be widely removed between transmitters and receivers that have a tone squelch function. .

[Brief explanation of drawings]

FIG. 1 is a time chart showing an embodiment of the present invention, and FIG. 2 is a time chart showing a conventional device.

Claims (1)

[Claims] An FM communication device with a tone squelch function, characterized in that transmission of a tone from a transmitter is stopped at the end of a call, and transmission high frequency output is stopped after an operation delay time of a tone squelch detection function of a receiver of the other party has elapsed.