The TX/RX100A wireless door chime entrance alert set is a commercial grade, USA Made door alert that will work on all door types (metal, aluminum, glass, steel, wood, Masonite, etc) without significant loss of range (up to 1000'). This digital PIR system operates without reflectors or light beam projectors and therefore is immune to false alerts caused by transient light. You can use it with doors open or closed. This Wireless Door Sensor/Transmitter is a self sufficient battery powered unit and does not require any electrical wiring. It operates on a AA batteries (not included). Mounting brackets are included for installation on door frames or casings but the unit is light enough to be installed on ceiling tiles above the door with double sided tape (not included). It can also be used on warehouse roll up doors, inside display cabinets, restricted area protection, or (patio, bedroom, bathroom) window alerting device. Double door operation is possible by placing the unit between the doors. The sensor transmits a wireless signal to the plug in receiver up to 1000' away from the unit so it is possible to cover large spans in retail stores, convenience stores, warehouses and industrial facilities. There are no limits to the number of receivers and transmitters that may be used in conjunction with each other as long as they are within range. There are four selectable tunes of "ding-dong" to choose from so you have the ability to distinguish what entry points are being accessed by selecting one of the four tones of "ding-dong" for each entry point. The chime receivers simply plug into a standard wall out and have an adjustable volume control from very loud to mute. The chime receiver has (1) 12 volt output which can be used to power virtually any 12 volt device such as a strobe, siren, bell, buzzer, etc and also a speaker output. This is convenient for very loud manufacturing facilities, cleaners, industrial plants, warehouses and any noisy environment.