Abstract: A fire detection system has a detector for sensing optical radiation from a spark or flame or hot spot and an optical waveguide comprising an elongate hollow tube, having an inlet end portion for placement in a hostile, hazardous environment, and having an outlet end portion for emitting light rays to the detector and for placement in a benign, non-hazardous environment, and having a reflective inner surface forming a passage for transmitting the optical radiation from the tube inlet end portion to the tube outlet end portion by successive internal reflections.The elongate hollow waveguide tube is sealed at the inlet end portion by a lens which admits the optical radiation to the tube; and at the outlet end typically by the detector. The sealed tube is filled with an inert gas, such as nitrogen, which helps to maintain the reflective interior surface of the tube.

Abstract: There is disclosed a condition responsive detection system and method comprising a length of optical fiber including a core-cladding material which has a modal dispersion ratio less than a predetermined number. The fiber is placed in the area to be monitored and is illuminated on one end by a source of radiant power. Electronic circuitry including a photocell are positioned at the receiving end of the fiber and detect when the radiant power transmitted by the fiber is reduced below a nominal level when the cladding material is altered, as for example by a fire or an overheat condition in the area being monitored. The reduction in radiant power received is due to the alteration of the cladding material such that the reflected radiant power is lost through the alteration in the material.

Abstract: There is disclosed a fire and explosion detection system and method comprising at least one first channel including a photocell and accompanying electronics for converting incident radiant energy of a first narrow band of wavelengths into a first electric signal; and, at least one type of second channel means including a photocell and accompanying electronics for producing a second electrical signal proportional to incident radiant energy of a second narrow band of wavelengths corresponding to background, black body emissions. The signal outputs of these two channels are further processed by a ratio detection circuit which produces yet another output electrical signal when the ratio of the two input signals exceeds a predetermined number. The output of this ratio detection circuit is further processed by a so called flicker frequency detection circuit which counts pulses indicative of the flicker frequency of the fire and gives a first warning if that flicker frequency exceeds a predetermined number.

Abstract: A test device for a multiple channel infra red detector utilizing photocells comprising an aperture plate mounted on the housing member of the detector. In the embodiment described a test lamp is mounted on a surface portion of the aperture plate in fixed relationship with two openings in the plate which are concentrically disposed about the two photocells. The test system utilizes the characteristic of the dual channel detector that the ratio of the response of each of the two cells to emissions in the infra red range (as received from a fire) is a certan value. The opening associated with one of the cells is larger in the path between the lamp and that cell so that more light energy impinges on it. The electrical energy to the lamp is increased until a level is reached where the ratio of the response of the one cell to the response of the other cell simulates the responses of the two when monitoring a fire. The warning system is triggered.