The InfraRed Dectector is an accessory to an InfraRed Relay and is used in a situation where you want a second receiver to cover a different area. The best example of this is a solid front door with a Detector on the outside connected to an IR Relay on the inside.The user can then open the door from either side.
Surface mounting, encapsulated with a 6m or 15m cable, outdoor or indoor.