Abstract: A flame detector which is capable of discriminating between hydrocarbon fires and background radiation produced by the sun, artificial light or black body radiation. Two radiation sensors are provided, each being responsive to separate known radiation peaks produced by a hydrocarbon fire. Logic circuitry is provided which produces an alarm signal only when the radiation received by each sensor is above a predetermined value, and when the radiation received by one specified sensor is greater than the radiation received by the other sensor.

Abstract: A fire detection system of the type utilizing an optical detector with discriminating photo-cells connected in series to form a voltage divider, with the rise in voltage at the junction of the photo-cells being utilized at the input to an amplifier to energize an alarm or activate an extinguishing system, in which a remotely controlled switch is provided for applying to the signal lead at the detector a test voltage from the remote end of the power lead at the detector, whereby both the continuity of the power lead, the continuity of the signal lead and the operativeness of the power supply are tested.