The FireAngel HW1-R heat alarm is mains powered with a replaceable 9V back-up battery, central silence button, and a dedicated test button. Up to 12 W1-R and W1-PF series alarms can be interlinked together via a dedicated cable, including the CW1-PF-T mains powered carbon monoxide alarm, to provide full coverage and reliable warning of possible danger throughout the premises. To ensure that there is a back-up in case of a mains power failure, these alarms also feature a 'safety clip' which prevents them from being fitted to the base plate without a battery. Two LED status indicators are located on either side of the alarm's test button, one of which will light up to indicate a fault or alarm when necessary and the other showing whether or not mains power is active. 230V mains powered with 9V alkaline back-up battery Dedicated test button Class A2 thermistor heat sensor; reacts to maintained temperatures between 54°C and 70°C Up to 12 W1 series alarms can be hard-wire interlinked