fire alarms

[my.apple.in.]

what is the principle ,working and construction of fire alarms?

[DaveH3]

Ok, here goes. Fire alarms consist of a detector/s, a control point and a sounder or sounders. The detectors could be manual as in a manual call point or automatic, these are just acting as a switch to trigger the alarm. You could have smoke detectors which could be ionisation detectors, optical detectors which detect the presence of smoke using a photo cell, beam detectors used in large auditorium, heat detectors mainly used in kitchens and thermal detectors sometimes used outdoors. A sprinkler when activated by heat also triggers the fire alarm system. Within the control point there is usually a back up battery in case the mains fail and modern systems are usually addressable i.e. they tell you which detector head has actually actuated. Hope this is of some help.