The Kidde K20C Professional Series Alarms can interlink with up to 23 inter-connectible alarms, which means that all alarms will sound if any detect smoke or heat. Detects visible fire particles associated with slow smouldering fires. It is 230 volt mains powered, with a battery back-up in the event of a power failure. A Hush™ button allows temporary silencing of nuisance alarms caused by cooking or steam and resets automatically. In addition, this button is used to check the alarm operation. A lock-out feature prevents the alarm from being attached/fitted unless the back-up battery is installed. The alarm has an impressive sound rating of 85 decibel at 3 metres. For convenience, it has a front-loading battery door to allow the battery to be changed without removing the alarm.