A simple burglar alarm circuits, sensors pyroelectric sensor IRA-E100SZI. When human movement is detected, the pressure on the electric buzzer alarm whistle. Sensor receives si
gnals via AC amplifier, and then by the rectifier circuit into a DC drive transistor VT1, VT2 when turned on. Piezoelectric buzzer alarm. Several nearby Hertz gain amplifier circuit requires about 70dB, single-stage amplifier is not enough, it can be multi-stage amplifier to ensure the necessary gain. When the input signal is generated by the body movement is very weak, the general use of the optical zoom system.