Wireless dual-tone electronic doorbell circuit diagram

Transmitting circuit: Press SB, the transmitting circuit works. D1, D2 and R2, R3, C4 form a low-frequency oscillator, which controls the audio oscillator composed of D3, D4, D5, and D6 to work alternately. The generated audio signal is added to the modulation end of the radio frequency signal oscillator through C7, and the ultra-high frequency oscillation signal is frequency modulated and then launched into the air.

Receiving circuit: After the FM wave induced by the antenna is demodulated by A2, a dual-tone doorbell signal is output from its 14-pin, which is coupled to the input of A3 via R7 and C26. At the same time, its 9-pin outputs a low level to cause the switch tube to V2 is turned on, A3 is powered on, and the audio signal is amplified and the sound is emitted by the speaker.