The proposed German magazine “Funkamateur” light relay is activated when light falls on the photoresistor R1 (see diagram) — when this occurs, a loud siren sound. Transistors VT1, VT2 equivalent odnoimennogo of the transistor included under the circuit of the sawtooth generator. The oscillator frequency is determined by the capacitance of the capacitor C1, the internal resistance of the photoresistor R1 and the resistor R2. Transistors VT3, VT4 included in the Darlington circuit, perform the function of the AF amplifier. It is possible to replace. Photoresistor — any domestic; transistors: VT1 – КТ3107, KT361, КТ203; VT2, VT3 blocking – KT315, КТ312; VТ4 – КТ503, КТ603, КТ815 with any alphabetic indexes.