JPS602705Y2 - public address telephone - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a public address telephone with a voice switch.

Generally, a sound switch is used in a public address telephone in order to prevent howling caused by sound coming from a speaker to a microphone.

This voice switch compares the transmitted and received signals and passes the higher level signal and attenuates the lower level signal to maintain the call quality of the loudspeaker telephone, but it has the following two problems. Ta.

One of them is that the voice of the speaker using the public address telephone is low.
Alternatively, if the speaker is too far away from the microphone, the audio switch may not work properly and the speaker continues to speak without being able to send a normal transmission signal to the other party, or conversely, the speaker may be too close to the microphone. In this case, a highly distorted transmission signal is sent to the other party, making it difficult to understand what is being said.
Second, if the speaker uses the loudspeaker in an environment where the ambient noise is louder than the allowable noise level, the received signal may not be reproduced at a sufficient volume than the speaker.
Additionally, the other party had to listen to the transmitted signal with a lot of ambient noise, making it difficult to hear.

The present invention is intended to solve the above problem, and its purpose is to provide a public address telephone that can easily inform the speaker of the level of the transmitted signal and the level of ambient noise when making and receiving calls. There is a particular thing.

In order to achieve the above object, a public address telephone according to the present invention is a public address telephone equipped with an audio switching circuit that compares the level values of a transmitting signal and a receiving signal to form a transmitting mode and a receiving mode. a noise detection circuit that is sensitive only to ambient noise among the audio signals that are transmitted; a display control circuit that operates based on the ambient noise signal of the noise detection circuit and the transmission signal that has passed through the transmission side audio switch;
It displays the appropriate level value and allowable noise value of the transmitting signal in advance, and further includes a level display that receives the output of the display control circuit and displays the transmitting signal and ambient noise signal during transmission and reception. It is composed.

According to the above configuration, it is possible to inform the speaker of the appropriateness or inappropriateness of the voice, and the purpose of the present invention can be completely achieved.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a loudspeaker telephone according to the present invention.

In the figure, the transmitting communication path is formed by a microphone 1, a microphone amplifier 2, a transmitting audio switch 4, a transmitting amplifier 5, a hybrid circuit 11, and a line terminal 12.

On the other hand, the receiving communication path is formed from the line terminal 12 via the hybrid circuit 11 to the receiving amplifier 6, the receiving audio switch 7, the speaker amplifier 9, and the speaker 10.

The audio switch circuit 3 includes a transmitting audio switch 4 for the transmitting and receiving channels, a transmitting amplifier 5, a receiving amplifier 6, a receiving audio switch 7, and a comparison circuit 8.

This embodiment uses these configurations to address the difference in the nature of the voice signal and the ambient noise signal among the transmission signals obtained from the microphone amplifier 2. In other words, the voice signal changes every moment, but the ambient noise signal is almost constant and continuous. A noise detection circuit 13 that detects only ambient noise signals by utilizing the difference in characteristics, a display control circuit 14 that operates based on the output of the transmitter amplifier 5 and the output of the noise detection circuit 13, and a display control circuit 14 that detects the level of the transmitter signal during a busy call. , a level display 15 is added which displays the level of the ambient noise signal, and also displays the transmitting signal appropriate level value and the allowable ambient noise level value.

In the circuit of this embodiment, when a voice is input to the microphone 1 and a receive signal is sent through the line, the transmit signal from the microphone amplifier 2 and the line terminal 12 are first sent in the audio switch 3.
, the hybrid 11, the reception amplifier 6, and the reception signal from the reception audio switch 7 are compared in a comparison circuit 8.

As a result of the comparison, if the transmitting signal is larger than the receiving signal, the comparison circuit 8 outputs a signal such that the transmitting audio switch 4 has a small loss and the receiving audio switch circuit 7 has a large loss,
The above-mentioned transmitting channel is formed by having a large transmitting channel gain and a small receiving channel gain within the switch.

Hereinafter, this state will be referred to as the transmitting mode.

On the contrary, when the receiving signal is larger than the transmitting signal, the receiving voice switch circuit 7
The comparator circuit 8 outputs an output so that the loss is small and the loss is large for the transmitting audio switch 4, and the receiving channel gain is large and the transmitting channel gain is small, thus forming the above-mentioned receiving channel.

Hereinafter, this state will be referred to as receiving mode.

On the other hand, the noise detection circuit 13 detects only the ambient noise signal among the transmission signals obtained from the microphone amplifier 2, and sends the ambient noise signal to the display control circuit 14 only in the receiving mode according to the output of the comparison circuit 8.

The display control circuit 14 mixes the output of the noise detection circuit 13 and the output of the transmitting amplifier 5 whose gain is controlled by the transmitting audio switch 4, but in the transmitting mode, the gain of the transmitting channel is large. Therefore, when in the receiving mode, the gain of the transmitting channel is attenuated and only the ambient noise signal is received, and the level indicator 15 is controlled by these signals.

The level display 15 displays the level of the transmitting signal in the transmitting mode and the level of the ambient noise signal in the receiving mode in accordance with the output level of the display control circuit described above.

In the receive mode, the receive channel gain is large and the receive signal is output from the speaker 10 and then input to the microphone 1, but this signal is not transmitted because the transmit channel gain is small. The output of the audio amplifier 5 is attenuated to a small level.

Furthermore, the output of the noise detection circuit 13 is not affected by the signal input from the speaker 10 to the microphone 1 because it is an audio signal, and only ambient noise signals are detected and output.

In this way, the transmitting signal and the ambient noise during transmission and reception are displayed on the level display 15.The one-way level display 15 displays the appropriate transmitting signal level value and the permissible ambient noise level value, respectively. , the speaker can conduct a normal conversation while looking at these displays.

As explained above, the present invention solves the problem of the speaker's transmitting signal significantly deviating from the appropriate level and continuing to transmit or using it in an environment where the ambient noise level exceeds the allowable ambient noise level by adding a level indicator, etc. This can be solved with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of a loudspeaker telephone according to the present invention. 1...Microphone, 2...Mic amplifier, 3...Audio switch circuit, 4...
・Transmission audio switch, 5...Transmission amplifier, 6.
...Reception amplifier, 7..Reception audio switch, 8..Comparison circuit, 9..Speaker amplifier, 10..Speaker, 11.・・・・・・
Hybrid circuit, 12...Line terminal, 13.
... Noise detection circuit, 14 ... Display control circuit 15 ... Bell display.

Claims (1)

[Scope of utility model registration request] Noise detection that is sensitive only to ambient noise among voice signals picked up by a microphone in a loudspeaker telephone equipped with an audio switch circuit that compares the level values of a transmitting signal and a receiving signal to form a transmitting mode and a receiving mode. a display control circuit that operates according to the ambient noise signal of the noise detection circuit and the transmission signal passed through the transmission side audio switch, and displays in advance an appropriate level value and an allowable noise value of the transmission signal; A loudspeaker telephone set further comprising a level display that receives the output of the display control circuit and displays a transmitting signal and an ambient noise signal during transmission and reception.