Magnetic contact via one-way radio, frequency 868Mhz. EN50131 Grade 2 Certificate. The High Security Unidirectional Wireless Door / Window Contact is a supervised transmitter ideal for the perimeter protection of doors / windows in residential applications and small businesses. The transmitter has a built-in magnetic contact and an additional zone input that can be connected to magnetic contacts or other wired sensors, which can be used for various control or safety applications. The RWT72M has an additional blade switch to detect anti-sabotage activities that is not included with the T72C. Any attempt to sabotage the detector with powerful magnets will cause a tamper alarm. CR123 3V lithium battery included. Compatible with RISCO™ unidirectional and bidirectional wireless systems.