55000-317- 65 STANDARD OPTICAL SMOKE DETECTOR. The optical smoke detector uses an internal pulsing LED and a photo-diode at an obtuse angle. The Series 65 Optical Smoke Detector incorporates a pulsing LED located within the housing of the detector. The external detector moulding is identical to that of the ionisation detector but has an indicator LED which is clear in quiescent state but produces a red light in alarm. As part of the Apollo Series 65 Detector Range the 55000-317 Optical Conventional Smoke Detector offers a fire detection solution to many applications.  The detector can be used with most modern conventional fire alarm panels.