This system consists of an infrared sensor to be installed next to the door, the window or near the stairs, and a receiver for easy wall mount. When the sensor picks up movement transmits a pulse to the receiver that will trigger a din don music (you can select tunes from the receiver 8). It will thus be alerted by a melody if someone tries to force the door, or if children are approaching or any danger to the stairs in your house. When the sensor detects a movement sounds the bell and makes light the blue LED of the receiver transmits up to 20m. Excellent to be installed at home, but also in the office, shop, trailer, garage, etc.. The range of the infrared sensor goes up to 8 meters, with a detection angle of up to 110 degrees. With melody selector on the receiver, and pulsating with power ON / OFF button on the transmitter. The sensor operates using 3 AAA 1.5 V batteries (not included), while the receiver runs on 3 AA 1.5 V batteries (not included). COLOR: White / transparent blue Sensor size: 65 x 80 x 40mm SIZE RECEIVED.: 107 x 120 x 40mm