Sound / Light Alarm Motion Senser Security Infrared Laser Alarm Switch DIY KitsDescription:How it works: In this study, the transistor as a switch.1: No alarm. When a laser is irradiated onto the photosensitive resistor, transistor ended, active buzzer power off, stop chirping; light off.2: Alarm. When the laser is blocked, no light exposure to the photosensitive resistor, the transistor is turned on, the buzzer to get the power starts singing while working indicator lights, sound and light alarm.The receiving end:The first pin connections: battery box red line, the buzzer anode (long pin), light emitting diode anode (long pin), photoresistor a pin.The second pin connections: Buzzer another pin, a light emitting diode cathode (short pin), the transistor first pin.The third pin connections: photoresistor another pin, pin a second transistor, the potential for a single side of the pin.The fourth pin connections: battery box black wire (ground), the third prong transistors, potentiometers two pins on one side of any one pin.The transmitter end:Laser head red wire to the battery box red line, the laser head in addition wire to the battery box black wire. Joints can be used to trap heat shrink tubing, then heated slightly to prevent short circuits.Note:Light shooting and different displays may causethe color of the item in the picture a little different from the real thing.The measurement allowed error is+/-1-3cm.We highly appreciate all custome rsopinions to improvethe selling, also if anything you unsatisfied, please contact us for probable best solution. Thank you!Package Included: 1Set Sound / Light Alarm Motion Senser Security Infrared Laser Alarm Switch DIY Kits(If there are any problems with the product, please send us pictures.Tell us more details about this problem)