What"s in the Package The driveway alert alarm kit comes with: 1 x Receiver 1 x Transmitter 3 x Wall Plugs 3 x Screws 1 x Instruction Manual How does it work? Basically, there are two parts to the Driveway Alert Alarm system. The Transmitter contains a passive infrared(PIR)sensor, which detects the moving heat created by an automobile"s engine(or any other noticeably hot object moving at sufficient speed). It can send signal to the receiver. The transmitter should be deployed outdoors, where it will have a clear view of the driveway. The Receiver mounts inside your home (or business, warehouse, shed, aircraft hangar, secret underground submarine docking station-where you need it, really, provided it"s within range of the outdoor unit). It contains a series of LEDs and a small buzzer to let you know when the outdoor unit detects motion. Technical Specifications A. Transmitter Power Requirements 3xAAA 1.5V battery(not included) PIR Sensor Viewing Area Approx.100 Degrees Horizontal PIR Sensor Range 24ft/8m approx.(varies by local conditions) Transmission Range 328ft/100m approx.(in the open air) B. Receiver Power Requirements 3xC 1.5V battery(not included) Chime Volume Approx.90dB General Guidelines Don"t mix battery types. For the best ongoing performance, we recommend using only fresh, high-quality, alkaline batteries.