With this top-quality Weatherproof Infrared Beam Motion Detector sensor you can provide extra security to your home by creating an invisible fence up to 70 ft. long outdoors (165 ft. indoors). Sold in pairs (transmitter and receiver) these sensors can be mounted anywhere inside or outside. Normally closed output (NC) with separate NC tamper output. Requires 10-30VDC 39mA power supply (sold separately). The twin beam, adjustable beam interruption time and automatic sensitivity adjustment of this unit minimize false alarms. The sensor will even work down to the point where 99% of the beam strength has been cut due to poor weather. Mount above pet height level and your pets can roam without setting off the alarm. Mounts to 1.66 diameter poles with included clamps or to any flat surface with screws. Additional units may be purchased to create an invisible fence around your entire property. Wires may be shared (see the manual for details and limitations). If you are looking for beam distances greater than 70'/165', check out the 130'/330' version. Incorporating automation This system can be used in conjunction with other products to create a lighting/chime alerting system. For a commonly used application check out this diagram for more information.