The outdoor weatherproof transmitter unit that can be either side or overhead mounted. A 9V replaceable battery is included and is already installed for your convenience. In the back of the unit there are six dipswitches. Numbers 1-4 control the communication security codes that must match the receiver. Numbers 5 & 6 on the transmitter identifies which of up to 4 transmitters (zones) is sending a driveway motion alert. There is an antenna that can rotate for optimal transmission to the receiver up to 1000' (LOS) or 600' recommended. The driveway beam projection at 25 feet is 1 foot square and at 50 feet it is 2 feet square.