JPS6027439Y2 - Voice switch control circuit device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an audio switch control circuit device that performs comparison control based on the ratio of two audio signals.

In voice telephones, that is, telephones that emit the received sound from the speaker, the sound played from the speaker is likely to be input again to the transmitting microphone, causing howling. Therefore, when the receiver's voice is louder than the transmitting sound, the device switches to receiving mode. On the contrary, when the transmitted sound is louder than the received sound, it is necessary to automatically switch to the transmitting mode and perform communication in one direction, and for this purpose, a voice switch control circuit device is required.

In conventional devices of this type, each signal is linearly amplified, then rectified and smoothed, and then levels are compared.

However, there were problems with the diode rectification of weak signals and the dynamic range caused by the upper limit of the circuit power supply voltage, and the operation was unstable regardless of whether the input signal was at a large or small level. .

The present invention solves these problems by providing a device that can control the audio switch in a good manner by comparing the ratio of two signals.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, 1 and 2 are terminals to which audio signals are input, 3 and 4 are logarithmic compression circuits, 5 and 6 are rectifying and smoothing circuits, respectively, and 7 is a comparison circuit having hysteresis characteristics.

8 is an output terminal.

Here, the comparison circuit 7 does not operate immediately when one of the input values to be compared becomes larger than the other input value, but when the one input value is a predetermined value higher than the other input value. It operates and generates an output when it becomes larger than the above value.

FIG. 2 shows a specific configuration of the logarithmic compression circuit 3 or 4, where 9 is an amplifier, and 10 and 11 are diodes connected with opposite polarities.

The input/output characteristics of the logarithmic compression circuit shown in FIG. 2 are as shown in FIG. 4, and the linearity is extremely good.

Next, the operation will be explained.

Audio signals applied to input terminals 1 and 2 are compressed by logarithmic compression circuits 3 and 4, respectively, and further processed by rectification and smoothing circuits 5 and 6.

The relationship between the audio signals input to the terminals 1 and 2 and the rectified and smoothed outputs of the circuits 5 and 6 is as shown in FIG.
A logarithmically transformed signal with good linearity is obtained.

The two signals compressed in this way are applied to the comparator circuit 7.

Note that this comparator circuit 7 compares two inputs, but because it has a hysteresis characteristic, it operates only when the difference in level between the two input signals exceeds a predetermined value.

The two input signals are each logarithmically compressed as described above, so whether the input signal levels are both low or high, they are compared to see if they exceed the predetermined level difference. be done.

Therefore, a comparison output can be reliably generated even when the signal level of each input is high.

3A is the input audio signal applied to the input terminal 1 or 2, and 3 is the output signal of the logarithmic compression circuit 3 or 4.

Further, in the figure, a shows the case of a high level audio signal, and b shows the case of a small level audio signal.

As is clear from the above description, according to the present invention, even if the signal is of a high level, a signal for controlling the audio switch can be obtained reliably, and the practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a voice switch control circuit device according to an embodiment of the present invention, Fig. 2 is a constituent country of the main parts, Fig. 3 is a signal waveform diagram of the main parts, and Figs. 4 and 5. Each figure is a characteristic diagram. 3.4...logarithmic compression circuit, 5,6...
Rectifier smoothing circuit, 7... Comparison circuit.

Claims (1)

[Scope of utility model registration request] first and second logarithmic compression circuits to which the first and second audio signals are applied, first and second rectifying and smoothing circuits to which the outputs of the first and second logarithmic compression circuits are applied, respectively; 1. An audio switch control circuit device comprising a comparison circuit having hysteresis characteristics for comparing the outputs of the second rectifying and smoothing circuit.