Dependable Magentic Contacts provide years of trouble-free operation. Compact transmitter can be easily mounted on any door or window frame. Anti-tamper switch immediately sets off alarm if cover is opened (WA400 system only). Low battery warning signal is displayed by the control panel (WA400 system only). Compatible with all Home Sentinel Security Systems. LOUD BURGLAR ALARM, WIERLESS SECURITY, ON SALE NOW.