External voice control mouthpiece of radio interphone without using batteries and background noise interference

摘要

The external voice control mouthpieces for radio interphones on the market receive voice signal under an open state. Therefore, the background noise is completely accepted and causes incorrect reaction. This invention uses a skin touch-controlled piezoelectric microphone because this kind of microphones receive voice signals under a closed state and thus are not interfered by the background noise. Furthermore, the piezoelectric microphone used in the present invention has the advantage of high sound wave voltage output without consuming any electric current. With a exclusively designed low power consuming voice control circuit, which merely obtains the power supply from the tiny electric current of the external capacity mouthpiece of the interphone. It thus achieves the goals of no batteries and no extra power.