With this whistle light switch you can turn on and off the lighting installation. The main part of this circuit is the UM3763 IC, produced by UMC. The piezo-ceramic buzzer is used here as a microphone and when it receives a tone frequency between 1.2 kHz and 1.8 kHz, the IC’s output will go HIGH. This means that the light will go ON if it was OFF, or go OFF it was ON.
For light control the UM3763 triggers a triac through T1. The supply voltage is taken directly from the main power supply. D1 and D2 diodes are used as rectifiers, and D3 limits the voltage at 3.9 V. D2 LED is used as an indicator of operating or idle state.
Because the whistle light switch circuit is powered from 220V you need to make good isolation and take good precautions.