The Danic DHA-2-RF 230V Interconnected Heat Alarm is supplied with a back up lithium battery that will last up to 10 years. This compact alarm, perfect when used in series with other RF connected alarms, is easy to install an includes a button for testing and silencing as well as a wireless remote control. Built to BS 5446-22003 Standard and certified by INTERTEK, Radio-interlinked smoke detectors and heat alarms are interlinked through radio-frequency RF signals. If one smoke alarm detects fire, all alarms go off. In the case of the battery operated radio-interlinked smoke alarms, no wiring is required at all.