The infra-red (PIR) detector turns the noise on when a warm body appears in the controlled area. This has an important purpose: researchers have found that cats can become desensitised to the noise if they realise that the noises are not associated directly with their presence in the controlled area. With the motion sensor, the cat learns to associate the noise with its own movement, and is much less likely to stop being afraid of the noise.
The PIR is attached to the main unit by a 10ft (3m) cable), receiving power from the main unit via this connection.
It has its own mounting bracket and up/down and lef/right swivel arm, allowing it to be pointed in the direction you need.

A red light comes on when the PIR is activated, allowing you to do a walk-through test to target the beam to a particular area of the garden.

Product Specification:
PIR unit is 4.5 ins high by 2.5 ins deep, by 3 inches wide.

Detection Range 30ft, through a 100 degree arc in both the vertical and horizontal. The repeller that this motion sensor is connected to emits ultrasonic sound that should be effective over 100ft.