JPH0254976B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an improvement of a signal selection receiving circuit of a slave station used in a selective calling method that selectively calls a plurality of slave stations using a single radio line. It is related to.

A selective calling method in which a master station selectively calls a plurality of slave stations is used in various fields.

For example, in the selective calling method used in disaster prevention and administrative radio systems, each city, town, and village broadcasts disaster prevention and administrative information to residents within their respective administrative areas using 60MHz radio lines.

Here, the method of selective calling is, for example, 382.5Hz~
2 of the waves allocated at 15Hz intervals out of 847.5Hz
A wave is selected and assigned to each area, and the master station sequentially transmits the two waves (called a calling signal) assigned to the desired area for one second each.

When the slave station detects the signal assigned to itself, the speaker circuit is connected, so disaster prevention and
Administrative information will be broadcast.

When the broadcast ends, a set signal is sent from the master station to turn off the speaker circuit, and this reset signal sound is emitted from the speaker.

For this reason, methods have been taken to reduce the noise to a level that does not cause any practical problems, but these methods have been insufficient in the case of outdoor loudspeaker systems.

Therefore, there is a need for a signal selection receiving circuit that does not cause the reset signal sound to be emitted from the speaker.

[Conventional technology]

FIG. 3 shows a conventional block diagram.

In the figure, received ringing signals A and B, each lasting one second, are applied from a terminal IN to signal detection units 1 to 3, which are comprised of lead filters.

Therefore, logic level detection signals are sent to the memory 4 from the signal detection units 1 and 2 that have detected the call signals A and B.
When the signal is sent to the gate circuit 7, a signal whose output has changed is sent from the memory section 4 to the gate circuit 7 according to the AND condition of the logic level information of A and B, so this circuit 7 operates, and the audio amplifier 6 and the speaker 8 are activated. Connected.

Therefore, information received from the master station after the calling signal is broadcast from the speaker.

Also, if there is no more information to broadcast, the master station will send out a reset signal R of, for example, 382.5Hz.
The memory section 4 is reset by the detection signal obtained by detecting this in the signal detection section 3. Therefore, the gate circuit 7 returns to its original state, and the connection between the speaker 8 and the audio amplifier 6 is disconnected.

In this case, it will take approximately 0.5 to 1 hour before the speaker shuts off.
There is a time delay of seconds (necessary to prevent audio malfunctions)
Therefore, a reset signal tone sounds from the speaker.

For this reason, the reset signal is blocked by, for example, about 30 to 40 dB by the band-elimination filter 5 to reduce the volume to a level that does not cause any problem in practical use.

[Problem that the invention seeks to solve]

As explained above, when a reset signal is detected and the connection between the speaker and the audio amplifier is disconnected, a reset signal tone is emitted from the speaker.

To prevent this, for example, a twin T-type band-elimination filter 5 is used to lower the level of the reset signal and suppress the ringing of the speakers due to this signal, but in the case of outdoor public address systems, only the level is lowered. That's not enough.

There are also two problems: if the speaker is connected immediately after the calling signal is detected, the calling signal may sound from the speaker.

[Means for solving problems]

The above problem consists of one or more signal detection sections that detect an inputted calling signal, a first delay circuit that delays at least one detection output of the one or more signal detection sections, and a first delay circuit that delays at least one detection output of the one or more signal detection sections. A detection signal from a signal detection unit that stores a predetermined detection output from one or more signal detection units when it is input, sends out a signal to turn on a gate circuit, and detects an input reset signal. a memory section that turns off the memory output when the first delay circuit and the output of the memory section are applied simultaneously; and a memory section that turns on when the output of the first delay circuit and the output of the memory section are applied simultaneously, and when the memory output turns off. A first gate circuit that is turned off, and a second gate circuit that is connected in series in response to the on/off of the first gate circuit.
This problem is solved by the signal selection receiving circuit of the present invention, which includes a delay circuit and a second gate circuit that turns on/off the connection between the audio amplifier part and the speaker.

[Effect]

In the present invention, a signal delay circuit is used in a band-elimination filter for blocking the reset signal, so that the time at which the reset signal is input to the audio amplifier is delayed by about one second. As a result, the reset signal is applied to the audio amplifier after the connection between the speaker and the audio amplifier is disconnected, so it is possible to prevent the speaker from ringing due to unnecessary signals.

Further, by turning off the second gate circuit for a certain period of time after detecting the ringing signal, the ringing of the speaker caused by the ringing signal was also prevented.

That is, it was possible to completely prevent the speaker from ringing due to the ringing signal and reset signal.

〔Example〕

The gist of the present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 shows a block diagram of one embodiment of the present invention, and FIG. 2 shows a time chart of FIG. 1.

In FIG. 1, a logic level detection signal obtained by detecting a call signal A applied to a terminal IN by a signal detection unit 1 is stored in a memory 4 and is delayed by a time T1 in a first delay circuit 9. After
It is added to the first gate circuit 10.

On the other hand, a calling signal B inputted subsequent to the calling signal A is converted into a logic level detection signal by the signal detection section 2, and is also stored in the memory 4. When the calling signals A and B are stored in the memory 4, the memory 4
The signal whose output has changed is sent to the second gate circuit 1.
Added to 0.

The first gate circuit 10 is turned on when the outputs from the first delay circuit 9 and the memory section 4 are applied simultaneously, and then the second gate 2 is turned on, so that the speaker 8 is turned on. It is connected to the audio amplifier 6 a time T1 after the signal A is detected.

Also, the voice input after the calling signal is processed through a second delay circuit 11 having a delay time of 1 second, and a voice amplifier 6.
It is broadcast from a speaker through.

On the other hand, since the logic level detection signal obtained by detecting the reset signal R applied to the terminal IN by the signal detection section 3 resets the memory section 4,
The first and second gate circuits 10 and 7 return to their original state, and the connection between the speaker 8 and the audio amplifier 6 is disconnected 0.5 seconds after receiving the reset signal.

At this time, the reset signal (continuing for 1 second) passing through the first delay circuit 11 is applied to the gate circuit 7 with a delay of 1 second, but since this circuit has already been restored, the reset signal will not leak from the speaker 8. No (see Figure 2).

〔Effect of the invention〕

As explained above, the present invention completely prevents the ringing of the speaker due to the ringing signal and the reset signal, and therefore has the effect of leading to improved services for the users.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure shows a time chart of FIG. 1, and FIG. 3 shows a conventional block diagram. In the figure, 1 to 3 are signal detection units, 4 is a memory unit, 6 is an audio amplifier, 7 is a second gate circuit, and 8
9 is a speaker, 9 is a first delay circuit, 10 is a first gate circuit, and 11 is a second delay circuit.

Claims (1)

[Claims] 1. One or more signal detection units that detect an inputted calling signal, a first delay circuit that delays at least one detection output of the one or more signal detection units, and one or more signal detection units that delay at least one detection output of the one or more signal detection units. When a predetermined detection output from the signal detection section is input, it is stored and a signal that turns on the gate circuit is sent out, and when the detection output is added from the signal detection section that detects the input reset signal, the memory is stored. a memory section that turns off the output; and a first gate circuit that turns on when the output of the first delay circuit and the memory output are applied simultaneously and turns off when the memory output is turned off. , a second delay circuit connected in series in response to the on/off of the first gate circuit, and a second gate circuit that turns on/off the connection between the audio amplifier section and the speaker. A signal selection receiving circuit featuring: