The Optex Wireless 2000 Door Contact / Wireless Transmitter is designed for indoor and outdoor use (not in direct rain). It can be installed on doors and windows. This Contact / Transmitter features a low battery signal and is powered by a CR123 3V lithium battery.The Door Contact/Wireless Transmitter is compatible with the Optex part # RC-10) and the Optex part # TR-10U. It can also be used as a wireless transmitter for the following Optex parts: VX-402R, BX-80NR, AX-100TFR, AX-200TFR, CX-702R, and the EX-35R.