EXTERIOR MOTION DETECTOR

 Exterior motion detectors are installed to protect the outside of your home; the places like driveways, front and backyards, sheds, swimming pools, carports and so on.
 The outside motion detector allows you to stop the burglar without having to confront him. You never know if the intruder has arms or how strong he is. Therefore, it is strongly recommended to call the police as soon as the intrusion in detected; do not confront them by yourself.
 There are a few types of motion detectors. Some of them respond to movement, and other respond to warm from bodied objects.

 The microwave motion detector [sensor} works by sending the microwaves on objects around it, and measuring the time that each microwave return. If a wave of different frequency of moving object in the covered area is returned, the alarm will sound. Special features can be added to that motion detector - so this motion sensor will not switch the alarm if your pet will enter the protected area.
  The infrared sensor measures the heat that is given off by an object that passes its monitored area. It then compares  against the background temperature. 
  Some of exterior motion detectors are supplied by the transmitter which unable the trespasser to detect it. However, in the same time the transmitter sends a signal to the main receiver being inside of the house. Thus, you can catch the unwelcome visitor, not allowing it to get into inside houses.