The condenser microphone fitted inside a position to catch the sound and generates AC signals, which pass by means of DC blocking capacitor C1 for the base of transistor BC549 (T1). Transistor T1 as well as transistor T2 amplifies the sound signals and delivers current pulses within the collector of T2. When audio is generated in front from the condenser mic, Triac1 (BT136) fires, activates the light plus the bulb (B1) glows for about two minutes.