Smoke detector Specification: 1. Battery operated: dc 9v. 2. Rechargeable lion battery 10 year 9 dc battery. 3. Photoelectric sensor. 3. Red led indicate alarm. Green led mains indicator light to confirm battery power supply 4. Test button, low battery alarm 5. Relay contacts-volt free with normally open and normally closed options and rated to 24 volts/1 amp resistive. 6. 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