JPH0420200A - Speaker output monitoring device for loud speaker device - Google Patents

Abstract

PURPOSE:To reduce equipment cost and to surely detect a sound output by inter posing the transformer of low impedance serially in a balance line, level- discriminating the secondary coil output of it and detecting the existence of the output of a sound loud speaking part. CONSTITUTION:When sound is outputted from a sound loud speaking part 6 and a current signal corresponding to a sound signal flows in a balance line 4, it is detected by an S/N coil 12, the sound signal corresponding to the current signal is supplied to an amplifier 7, is amplified and after that, is supplied to a sound signal detector 8. In this case, the S/N coil 12 is inter posed serially in the balance line 4, is a constitution able to flow a large current to a primary side and is low impedance to the sound signal. Thus, since the output of the S/N coil does not exist when any part of the balance line is broken, it can be detected surely whether sound is outputted or not with suppressing equipment cost low.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a speaker output monitoring device for a public address system that is used by being attached to a speaker system that transmits information through loudspeakers, such as disaster prevention radio, dam warning systems, etc. Regarding.

(Prior Art) An audio information transmitting device that notifies information such as a warning by outputting a message transmitted through a wireless communication facility such as a disaster prevention radio or a dam warning system from a loudspeaker. A system shown in FIG. 2 is conventionally known as a system that includes a speaker output monitoring device for confirming that the .

The audio information transmission device shown in this figure includes a receiving device tloI that demodulates a radio signal from a monitoring device (not shown) received by an antenna 102 installed on a mast or a steel tower, and outputs an audio signal. A speaker amplifier +03 that amplifies the audio signal and a balance line 10 that transmits the audio signal amplified by the speaker amplifier 103.
an audio amplification unit 106 such as a trumpet speaker that converts the audio signal supplied via the balance line 04 into sound and outputs it as sound; and an amplifier +07 that amplifies the output of the speaker amplifier 103.
An audio signal detector 108 that rectifies the output of the amplifier +07 to detect the presence or absence of an audio signal, and the audio signal detector 1
A transmitting device 110 that generates a wireless signal according to the output of 08.
and an antenna 109 for transmitting a wireless signal output from the transmitting device 11O to the monitoring device side.

In this audio information transmission device, when a wireless signal transmitted from the monitoring device side is received by an antenna 102, the receiving device 101 demodulates the wireless signal, reproduces an audio signal, and outputs this as audio from an audio amplification unit 106. At the same time, it is detected whether or not audio is being output from the audio amplification unit +06, and the detection result is converted into a wireless signal and transmitted from the antenna 109 to the monitoring device side.

However, in such an audio information transmission device, it is determined whether or not audio is being output from the audio amplification unit 106 based on the signal voltage between the output and end of the speaker amplifier 103 and the ground. As shown in FIG. 3, even when part P of the balance line 104 is disconnected and no sound is output from the audio amplification unit 106, as long as the audio signal is output from the speaker amplifier 103, the audio will continue to be output from the audio amplification unit +06. There was an inconvenience that the detection result was erroneously detected if it was being output and was transmitted from the antenna 109. If such false detection occurs, the message will not be transmitted and the purpose of preventing damage due to accidents, disasters, etc. cannot be achieved.

In order to solve this problem, an audio information transmission device as shown in FIG. 4 has been developed.

The audio information transmission device shown in this figure is provided with a microphone 111 near the audio amplification unit 106, and the microphone 111 collects and detects the audio output from the audio amplification unit 106, which is then transmitted to the amplifier 10 via an answer back line 112.
7, it is detected whether or not audio is being output from the audio amplification unit 106, and the detection result is transmitted from the antenna 109.

Therefore, in this audio information transmission bag E, when the balance line 104 is disconnected and no audio is output from the audio amplification unit 106, this is reliably detected and the detection result is sent to the antenna +
It can be sent from 09.

However, in such a voice information transmission device,
Since the microphone I11 must be installed near the audio amplification section 106 and the answer back line 112 must be installed, there is a problem in that the equipment cost increases.

(Object of the Invention) The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and it is possible to relatively reliably detect whether or not audio is being output from an audio amplification unit while keeping equipment costs low. It is an object of the present invention to provide a speaker output monitoring device for a public address system.

(Summary of the Invention) In order to solve the above-mentioned problems, the present invention provides a speaker output monitoring device for a public address system that supplies a signal from an output transformer of a power amplifier to an audio loudspeaker unit via a balance line. In a speaker output monitoring device,
The present invention is characterized in that a low impedance transformer is inserted in series in the balance line, and the level of the output of the secondary coil is discriminated to detect the presence or absence of an output from the audio amplification section.

(Examples) Hereinafter, the present invention will be described in detail based on illustrated examples.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The audio information transmission device shown in this figure includes a receiving device 1 that generates an audio signal by demodulating a wireless signal from a monitoring device (not shown) received by an antenna 2 installed on, for example, a banza mast or a steel tower. , this receiving device 1
a speaker amplifier 3 that amplifies the audio signal output from the speaker amplifier 3; a transformer 5 that sends the audio signal amplified by the speaker amplifier 3 onto the balance line 4; A signal obtained from an audio amplification unit 6 such as a trumpet speaker that outputs a an amplifier 7 that amplifies the output of the amplifier 7, an audio signal detector 8 that rectifies the output of the amplifier 7 to detect the presence or absence of an audio signal, and a transmitter 10 that generates a wireless signal according to the output of the audio signal detector 8. , this transmitter 1
0 to the monitoring device side.

Next, the operation of this embodiment will be explained with reference to FIG.

First, the wireless signal transmitted from the monitoring device side is transmitted to the antenna 2.
When the signal is received by the receiver, the receiving device l demodulates the signal to reproduce the audio signal, and after amplifying it by the speaker amplifier 3, supplies it to the audio amplification unit 6 via the transformer 5 and the balance line 4 to reproduce the audio signal. output.

Furthermore, when a sound is output from the sound amplification section 6 and a current signal corresponding to the sound signal flows through the balance line 4, S
This is detected by the /N coil 12 and an audio signal corresponding to the current signal is supplied to the amplifier 7 and amplified, and then supplied to the audio signal detector 8.

Thereby, the audio signal detector 8 rectifies the output of the amplifier 7 to detect the audio signal, and supplies this detection result to the transmitting device tlO to generate a wireless signal and transmit it from the antenna 9 for the monitoring. It is transmitted to the device side.

Here, the S/N coil is a coil that is traditionally inserted into the power line of in-vehicle radio equipment, etc., and is made to remove vehicle ignition noise or generator noise that enters the communication equipment via the power line. This is a transformer that allows a large current to flow with a relatively small inductance.

Therefore, above 8c in the present invention! The S/N coil is
Similarly, any device can be used as long as it has a configuration that allows a large current to flow through the primary side and has a low impedance for audio signals.

As described above, in this embodiment, the S/N coil 12 inserted into the balance line 4 detects the current flowing through the balance line 4 and determines whether or not audio is being output from the audio amplification section 6. Since it is detected, if any part of the balance line is disconnected, S/
Since the output of the N coil is eliminated, it is possible to relatively reliably detect whether or not audio is being output while keeping equipment costs low.

In addition, when the output of the audio amplification unit 6 is set to 100W to 240W and the input impedance is set to about 50Ω, a normal transformer is inserted in the balance line 4 to detect the current flowing through the balance line 4. In this case, a device with a large capacity must be used, which is very disadvantageous in terms of cost and mounting space. The coil 12, that is, the inductance is 1 mH ~
Since a current of about 2 mH is used, the cost and space of the entire device can be reduced.

Furthermore, in the embodiment described above, the current flowing through the balance line 4 is detected by the S/N coil 12, but even if a transformer with an extremely small inductance is used, the same effect as in the embodiment described above can be obtained. Obtainable.

(Effects of the Invention) As described above, according to the present invention, it is possible to reliably detect whether audio is being output while keeping equipment costs low.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an audio information transmission device using an embodiment of a speaker output monitoring device for a public address system according to the present invention;
Fig. 2 is a block diagram showing an example of a conventionally known audio information transmission device, Fig. 3 is a block diagram for explaining the problems of the audio information transmission device shown in Fig. 2, and Fig. 4 is a conventional one. FIG. 2 is a block diagram showing another example of the audio information transmission device known from the Japanese company. 3... Power amplifier (speaker amplifier), 4... Balance line, 5... Output transformer (transformer), 6...
...Audio amplification unit, 8...Audio signal detector, 12...
Transformer (S/N coil).

Claims (1)

[Claims] (1) In a speaker output monitoring device of a public address system that supplies a signal from an output transformer of a power amplifier to an audio amplification unit via a balanced line, a low impedance transformer is inserted in series in the balanced line, and 1. A speaker output monitoring device for a loudspeaker, comprising means for detecting the presence or absence of an output from the audio amplification section by level-discriminating the output of the next coil.