JPH0548706A - Loudspeaker telephone system - Google Patents

Abstract

PURPOSE:To prevent howling by repeatedly turning OFF a reception channel when a transmission channel is ON and turning On the reception channel when the transmission channel is OFF at a constant period and to maintain simultaneous communication performance by shortening the period. CONSTITUTION:In speech mold, a transmission switch 5 is turned on by a transmission/reception switch control circuit 7, a signal inputted from a microphone passes through a microphone amplifier 3 to become a transmission output, and a reception switch circuit 6 turns OFF, so that a reception input is not sent to a speaker 2. In reception mode, on the other hand, the circuit 7 turns OFF the switch 5, the signal inputted to the microphone 1 is not led out, and the circuit 6 turns ON at the same time, so that the reception input 14 is passed through a speaker amplifier 4 and outputted to the speaker 2. The speech mode and reception mode are repeated at the constant period to completely suppress the howling. Further, the switching period is shortened to secure simultaneous communication performance while a feeling of switch is eliminated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a loudspeaker telephone system, and more particularly to a loudspeaker telephone system having a howling prevention function.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a conventional public address telephone system. The transmission output from the microphone 1 is input to the transmission variable loss circuit 11 via the microphone amplifier 3, the loss amount is controlled, and the transmission output 13 is obtained.

Further, the reception input 14 is the reception variable loss circuit 1
The loss amount is controlled by 2 and is supplied to the speaker 2 via the speaker amplifier 4.

The output of the microphone amplifier 3 has its transmission level detected by the transmission detection rectifier circuit 8, and the speaker amplifier 4
The reception level of the reception input is detected by the reception detection rectification circuit 9. The voice switch control circuit 10 operates in accordance with these detection outputs, and controls the loss amounts of the transmission variable loss circuit 11 and the reception variable loss circuit 12.

That is, in this device, in order to prevent howling, the voice switch control circuit 10 compares the output of the transmission detection rectifier circuit 8 and the output of the reception detection rectification circuit 9 to determine the transmission detection rectification circuit 8. When the output is large, it becomes the transmission mode, and the loss circuit 12 is inserted in the speech path of the reception,
When the output of the reception detection / rectification circuit 9 is high, the reception mode is set, and the loss circuit 11 is inserted into the communication path of transmission.

[0006] In the conventional loudspeaker system, howling is prevented by adding a loss to the speech path of the receiving voice in the transmitting mode and a loss in the transmitting voice in the receiving mode. Therefore, howling can be prevented if the insertion loss is large,
In the transmitting mode, the receiving level becomes low and the simultaneous communication property deteriorates.

Further, if the amount of loss to be inserted is small, simultaneous talkability is improved, but there is a problem that howling is likely to occur.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a loudspeaker system capable of effectively preventing howling and ensuring simultaneous communication.

[0009]

A loudspeaker system according to the present invention comprises a voice transmission switch means for turning on / off a voice transmission input, a voice receiving switch means for turning a voice receiving input on / off, and the voice transmitting switch means and the voice receiving switch means complemented at a constant period. And a control means for performing on / off control.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and the same portions as those in FIG. 2 are designated by the same reference numerals. In the transmitting mode, the transmitting / receiving switch control circuit 7 turns on the transmitting switch circuit 5, and the signal input from the microphone 1 passes through the microphone amplifier 3 and becomes the transmitting output 13. At the same time, the reception switch circuit 6 is turned off, and the reception input 14 is not output to the speaker 2.

In the reception mode, the transmission switch circuit 5 turns off the transmission switch circuit 5, the signal input to the microphone 1 is not derived, and at the same time, the reception switch circuit 6 turns on. Nari, listening input 14
Is output to the speaker 2 through the speaker amplifier 4.

The switching between the transmission mode and the reception mode is repeated by the transmission / reception switch control circuit 7 at a constant cycle.

Since howling is generated when the output of the speaker 2 is fed to the microphone 1, as described above, the transmitting / receiving switch control circuit 7 complementarily turns on / off the transmitting switch circuit 5 and the receiving switch circuit 6. By doing so, when the input of the microphone 1 is output, there is no output of the speaker 2, and when the reception input 14 is output from the speaker 2, the output of the microphone 1 is not sent out, so howling can be suppressed completely. .

The switching cycle between the transmission mode and the reception mode is set so as not to cause discomfort due to the switching. At this time, the switching cycle cannot be unambiguously specified due to the positional relationship between the microphone and the speaker, the indoor conditions, etc., but at least the voice frequency (for example, 300 Hz to 3 KHz for a loudspeaker telephone).
2) or a frequency corresponding to more than twice, and as an example, it is preferable to switch at a frequency of about 10 KHz.

Further, by shortening the switching cycle, it is possible to eliminate the feeling of switching and ensure the simultaneous communication.

[0017]

As described above, according to the present invention, when the transmission call path is on, the reception call path is off, and when the transmission call path is off, the reception call path is on. Since it repeats at a constant cycle, howling can be prevented from occurring due to the wraparound of the microphone and the speaker, and simultaneous talking can be ensured by shortening the cycle. Therefore, it is possible to provide a loudspeaker telephone device having a simple configuration and excellent characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional public address telephone device.

[Explanation of symbols]

 1 Microphone 2 Speaker 3 Microphone amplifier 4 Speaker amplifier 5 Transmission switch circuit 6 Reception switch circuit 7 Transmission / reception switch control circuit

Claims (1)

[Claims] 1. A transmission switch means for turning on / off a transmission input, a reception switch means for turning on / off a reception input, and a control means for complementary on / off control of the transmission switch means and the reception switch means in a constant cycle. A loudspeaker telephone device characterized by including.