Apollo Series 65 smoke & heat detector range are a direct replacement for the earlier Series 60 devices.
Series 65 have a wide voltage range (9-33 volt DC)
and can be integrated on to security systems when used with the 12 volt relay base (45681-508)
Optical Smoke Detector
The optical smoke detector uses an internal pulsing LED and a photo-diode at an obtuse angle.
In the event of smoke entering the chamber, the light pulse from the LED will be scattered
and registered by the photo-diode. The detector will then enter the alarm state and the indicator LED lights up.