Automatic watch anti-theft alarm circuit

Shown is an automatic watch anti-theft alarm circuit , which is mainly used for automatic night watch in homes, warehouses and other occasions. The
circuit is mainly composed of pyroelectric infrared sensor , light control circuit (RG, RP2, R4), alarm drive circuit (IC2 and foreign components)
, etc.
    When the light intensity is high during the day, the photoresistor RG is in a low resistance state, the transistor VTI is turned on, and the ④ pin of the alarm circuit is short-circuited: at
night - the RG resistance value becomes larger, VT1 is cut off, and the subsequent alarm circuit enters the alarm ready state. When someone enters the area detected by the pyroelectric infrared sensor
, the ICI② pin is triggered and the buzzer sounds an alarm.