This kit is ideal for getting started monitoring your home or business. It includes one battery powered sensor and a 3-zone chime receiver with relay output. The receiver can be expanded to monitor up to nine sensors (3 per chime) or get a second receiver later so you'll hear the chime when a sensor detects motion. The kit also includes mounting screws for the sensors and chime receivers plus an AC adapter to power the receiver. You'll only need a 9-volt battery for the sensor. # Wireless Visitor Announcement System # 1 Wireless Indoor/Outdoor Motion Sensor # 1 Chime Receiver with Relay # 1 AC adapter for chime receiver # Mounting screwsSimply place the weatherproof PIR Motion Sensor alongside the entrances to your home. When a vehicle or person crosses the sensors path, the sensor sends a signal to the indoor remote Chimebox Relay. Additional Wireless Motion Sensors are available for expanding this system. Trigger your Wireless Visitor Announcement System or or 3-Channel Receiver Chimebox w/Relay manually using a Wireless Handheld Transmitter (sold separately). You may also trigger the chime manually with the Wireless Hand-Held Transmitter.