JPS61161896A - Automatic switch circuit of microphone - Google Patents

Abstract

PURPOSE:To prevent the sending out of the external noise by providing a sensor microphone besides a main microphone and controlling a by-pass circuit of a main microphone by the result to compare the level of the signal of both microphones. CONSTITUTION:To a main microphone 1M, an amplifier 2M and an alternating current-direct current converting circuit 3M are successively connected, and the first signal system is obtained. Also to a sensor microphone 1S, an amplifier 2S and an alternating current-direct current converting circuit 3S are successively connected, and the second signal system is obtained. The direct current signal output of both systems are applied to a comparing circuit 4, the level is compared, and in accordance with the comparing results, transistors 7 and 8 are controlled by on and off. The transistor 7 is connected through a capacitor 9 to an output end of the amplifier 2M, and by turning on this, a by-pass circuit of the signal, which occurs at the microphone 1M, is formed. As the result, the sending out of the external noise is prevented.

Description

[Detailed Description of the Invention] (Technical Field) When using a microphone in an environment where noise is expected to be generated, such as outdoors, when there is no audio signal to be transmitted, the connection with the amplifier section is essentially disabled. This invention relates to a microphone autoswitch circuit that prevents external noise from being transmitted.

(Technical background) When a microphone is used in a noisy or windy place, only external noise and unnecessary voices are amplified from the time the microphone is turned on until the user starts speaking, or when the user stops speaking. This is extremely jarring.

To avoid this situation, turn on the microphone,
Although it is possible to manually turn off the switch by frequently operating the switch, it is not possible to reliably eliminate external noise, and it is extremely troublesome.

(Object of the Invention) An object of the present invention is to provide a microphone auto-switch circuit that automatically allows substantial connection to an amplification section only when there is a signal such as voice to be transmitted.

(Summary of the invention) The present invention provides a sensor microphone in addition to the main microphone, amplifies the signals generated by both microphones individually, performs AC-DC conversion, and then compares the levels of both DC signals. When the signals generated in the main microphone are equal, the transistor that forms the signal nozzle/gauss circuit is turned on, and when they are different, it is turned off, and when there is no signal to be transmitted (audio signal, etc.), the connection with the subsequent amplifier section is disconnected. It is designed to substantially cut off and prevent external noise from being transmitted.

(Embodiment) The drawing shows an embodiment of the present invention, where IM is a main microphone, IS is a sensor microphone, 2M and 2
S is an amplifier, 3M and 3rd are AC-DC conversion circuits, 4 is a comparison circuit (operational amplifier), 5 and 6 are resistors, 7 and 8 are transistors, and 9 and 1O are capacitors.

The main microphone IM has an amplifier 2M and an AC
The DC conversion circuit 3M is connected in sequence to make it the first signal system, and the amplifier 2S and the AC-DC conversion circuit 3 are connected in order to the sensor microphone 1st, making it the second signal system. . The DC signals of both systems, that is, the outputs of the AC-DC conversion circuits 3M and 3S, are applied to the comparison circuit 4 to compare the levels, and depending on the comparison result, the transistors 7.8 are turned on.

I try to control off. For example, when both DC signals are equal, it is turned off, and when they are different, it is turned on.

The transistor 7 has a collector connected to the capacitor 10.
are connected to the output terminal of the amplifier 2M through the capacitor 9, and to the terminal to through the capacitor 9, and their emitters are grounded. When there is no audio signal or the like to be transmitted, the potential of the terminal to to which the subsequent amplifier section is connected is forcibly set to approximately ground potential to prevent external noise from being transmitted. That is, by turning it on, the connection with the amplifying section is substantially cut off.

The transistor 8 is an open collector, and can be used for other controls, such as a standby switch for a transceiver, a level switch as a sensor, and a language LL.
Used as a tape stop switch, etc. Similarly to the transistor 7, this transistor 8 is also controlled to be turned on or off by the output of the comparator circuit 4.

Next, the operation will be described. When you start speaking using the main microphone IM, the audio signal is amplified by the amplifier 2M, and converted into a DC signal according to the magnitude of the input AC signal by the AC-DC converter circuit 3M, which is sent to one input terminal of the comparison circuit 4. join. At this time, if there is external noise, it will be detected by both microphones, and it will be superimposed on the aforementioned audio signal to generate a DC signal in the second signal system, which will be applied to the other input terminal of the comparator circuit 4. During use, its level is lower than that of the first signal system, and a level difference occurs between the two systems. As a result, transistor 7.8 is turned off and the signal of main microphone IM appears at terminal to. In other words, the sound is amplified and amplified by the amplification section in the subsequent stage.

If the conversation stops and only external noise is sensed, the level of the DC signal in both systems will be equal, and the transistor 7.8
turns on. When the transistor 70 is turned on, a pin bus circuit for the signal of the main microphone IM is formed. In other words, the downstream amplifier section is cut off, and external noise is prevented from being transmitted.

(Effects) As described above, according to the present invention, a sensor microphone is provided in addition to the main microphone, and after amplifying the signals generated in both microphones and performing AC-DC conversion, the levels of the DC signals are compared and the results are obtained. Since the transistors that form the main microphone signal piecing circuit are turned on and off depending on the signal, amplification is possible only when there is an audio signal to be transmitted, and external noise can be amplified during intervals. It can definitely be prevented. Therefore, this is particularly effective when used in a noisy place, for example when a loudspeaker is mounted on a motorcycle, since unnecessary noise is not spread. Also, if you add a transistor that operates similarly to the transistor for the Bino bus,
Related control becomes possible.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of a microphone autoswitch circuit according to the present invention. IM... Main microphone, IS...
・Sensor microphone, 2M and 2S...Amplifier, 3M and 3S...AC-1DC conversion circuit, 4.
...Comparison circuit, 7 and 8...Transistor.

Claims (1)

[Claims] a first signal system that is connected to the main microphone and performs amplification and AC-DC conversion of the signal; a second signal system that is connected to the sensor microphone and performs amplification and AC-DC conversion of the signal; 1. A comparator circuit that compares the level of the DC signal of the second signal system, and is controlled by the output of this comparator circuit, and is turned off when both DC signals are equal, and turned on when they are different. and a transistor forming a bypass circuit for the generated signal.