Radio module for use in the Busch-Smoke Alarm®/Heat Alarm (6833/01-84 and 6835/01-84). For wireless networking of up to 20 radio devices. Tested according to VdS Directive 3515. Suitable for connecting the Busch-Smoke Alarm®/Heat Alarm to external systems such as Busch-free@home® in combination with the Busch-free@home®Alarm Stick. With built-in lithium battery. Battery life at least 10 years. Radio frequency: 868 MHz Range: max. 100 m outdoors, max. 30 m indoors.