.. ... \n4 x FireAngel SW1-PF-T Mains Powered Optical Smoke Alarms with 9V Back-Up Battery\nThese alarms can be installed, along with linked heat alarms (if required), to provide a fire detection system to comply with British Standard BS 5839: Pt.6 Grade D System incorporating one or more interlinked mains powered smoke alarms and heat alarms (if required), each with an integral stand-by supply. Wiring requirements:- 1.0mm or 1.5mm 6242Y Twin & Earth cable to the first alarm position, then 1.0mm or 1.5mm 6243Y 3 Core & Earth cable from the first alarm position to the second alarm and so on in a \""radial\"" or \""daisy chain\"" type circuit arrangement. Suitable for use within hallways and landings, as well as living rooms and bedrooms. Should not be interconnected with any other brand / range of alarms.\n--Mains voltage 230/240V AC 50Hz\n--Replaceable PP3 9V battery back up\n--High performance optical detector\n--Large central test and silence button\n--Push fit base for quick am