1.Battery operated: DC 9V. 2.Rechargeable li-ion battery 10 year 9 DC battery. 3.Photoelectric sensor. 4.Red LED indicate alarm. Green LED mains indicator light to confirm battery power supply 5.Test button, Low battery alarm 6.Relay contacts-volt free with Normally open and Normally closed options and rated to 24 volts/1 amp resistive. 7.Alarm supplied with ¡° connector plug¡± for easy of installation ,built in sounder to give a minimum sound output of 85 dB at 3 m senses smoke using the light scatter principle-quick response to visible smouldering smoke, test button simulates smoke- use to check performance at least monthly, option current <10uA, alarm current<30 UA. 8. Standard compatiabl:ISO 12239, EN 54-7, BS 5446-1, EN 50134-2, I-ETS 300220. Contact:jacob@autosecu.com MSN:jacobhu1984@hotmail.com