Mains-powered heat alarm that can be interlinked with up to 23 other Kidde mains alarms, optical or heat. Once interlinked, detection of the relevant danger by an individual unit will sound across all connected alarms. Alarm memory identifies source unit within the network. For use in humid or dusty environments where an optical or ionisation smoke alarm is unsuitable. Ideal for kitchens, loft spaces and garages. Combined test/hush button allows regular alarm testing and can be used to temporarily silence nuisance alarms. Features tamper-resistant locking device to prevent unauthorised removal without use of a tool. Requires installation by a professionally qualified electrician. Fixings supplied. Interlinked when Hardwired 230V AC/DC Mains-Powered with Battery Backup Replaceable Battery (Alkaline) 85dBA Alarm at 3m Test/Hush Button Interlinked when Hardwired 230V AC/DC Mains-Powered with Battery Backup Replaceable Battery (Alkaline) 85dBA Alarm at 3m Test/Hush Button