Talking Electronics

Microwave sensors send out ultra high frequency sound waves, and detect the reflections. If someone walks near the sensor (range adjustable onboard), they will start to reflect the microwaves. The receiver detects the change in reflections, and if the object remains within the microwave field for a length of time (depending on the input delay on the alarm it is used with), it will trigger the alarm after a few seconds or straight away. It has an maximum effective range of 3m. It incorporates a sensitivity adjustment to help avoid false alarms. 12v DC input. The output is negative when triggered.