Wire free and easy to install. Detects movement within the home and activates alarm when movement is detected. Size (H)9.5, (W)6.5, (D)4cm. Weight 65g. Requires 1 x 9V PP3 battery (included). The PIR detector is only compatible with Friedland response multi user alarm (700/2740), Freidland response multi function alarm (700/2757) & Friedland response telecommunicating alarm (700/2764) and not standard wireless alarm (700/2733).