TrueAlarm photoelectric sensors use a stable, pulsed LED light source and a silicon photodiode receiver to provide consistent and accurate smoke sensing with low power requirements. Seven levels of sensitivity are available for each individual sensor, ranging from 0.2% to 3.7% per foot of smoke obscuration. Sensitivity is monitored and selected at the fire alarm control panel. The sensor head design provides 360° smoke entry for optimum response to gray or black smoke from any direction. A built-in screen keeps insects from entering the smoke chamber. Due to its photoelectric operation, air velocity is not a factor, except as it affects area smoke flow.