Multi-Tech motion sensors use a combination of infrared sensing with technology that detects the motion of physical objects. The most common method is to use micro-waves. The motion sensor transmits micro-waves and then "listens" for a change in the echo by using the doppler effect. Only when a motion sensor detects the movement of heat between zones AND senses the physical movement of an object in the protected area will an alarm occur.
Unlike a "Passive Infrared Sensor" which only responds to the energy received, a duel tech device sends out energy. The amount of energy transmitted must be adjusted to the size of the protection area. Too much energy will result in room saturation and can either reduce the detection effectiveness or make it too sensitive. An installer should calibrate the micro-wave to the lowest level that still provides the detection protection desired. Refer to the motion sensor installation manual for each model you are installing.