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 device employing ionization principles for fire detection disclosing a configuration which allows compensation for adverse effects due to the flow of the gas through the device or due to the accumulation of dust and dirt therein. The detecting device includes two ionization chambers, each having a first member, such as a cylindrically shaped cup, having first and second conductive surface portions. Each chamber also includes a second member, such as a circular, electrode disc having two conductive surface portions. There is disposed in each chamber a radioactive source for ionizing the gas in the volumes intervening between respective pairs of surfaces. The area dimensions of the respective pairs of surfaces, the intervening volumes and the distances there between, and the relative orientation of the respective pairs are calculated and placed such that the ionization currents flowing between pairs of conductive surfaces are substantially equal and orthogonal to each other.

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.

Abstract: An ultraviolet fire detection device using a phosphor to translate energy from ultraviolet wavelengths down into visible and near infrared wavelengths for detection by a photosensitive solid state device, sounding an alarm upon detection of ultraviolet wavelengths associated with flames. In one embodiment has two windows, a reference window being opaque to ultraviolet wavelengths. In the second embodiment, a prism or diffraction grating is used to separate the light source into its various wavelengths.

Abstract: An electronic switch for use in alarm circuits in which line polarity is reversed in the actuation mode such that the electrical continuity of the circuit and the loads in the circuit may be supervised in series and upon polarity reversal the loads may be actuated in parallel. A first embodiment for Class B circuits uses three diodes to steer a current flow from the positive line to the load and back again supervising each load and a field loop in series. Upon polarity reversal, the diodes steer full terminal voltage to each load in the loop. A second embodiment for Class A circuits utilizes a transistor to short out one diode so that current may flow in either direction along one line in the event of a break in that line.

Abstract: A capacitive shift fire detection device having a sample circuit and a reference circuit, each circuit having an air capacitor connected to an oscillator and a counter. The presence of particles of combustion in the ambient environment results in a change in the dielectric constant of the air dielectric of the sample capacitor, thus changing its capacitance. This change in capacitance is detected by an oscillator in the sample circuit, the mismatch of oscillators in the two circuits causing an exclusive OR-gate to go high, activating an alarm system.

Abstract: A three wire circuit for supplying electrical power to active, power-consuming detection devices and communicating electrical signals providing supervisory information and fire alarm information to a control panel. Two wires supply electrical power the third carrying supervisory and alarm signals. Passive non-power-consuming detectors may also be utilized on said circuit. Detection devices switch the positive power to the signal wire in the event of an alarm and an end-of-line device switches the negative power to the signal wire through a current limiting device as a supervisory signal when conditions are normal. The end-of-line device measures the voltage on the power supply wires and opens its switch when the voltage falls below a specific level to indicate trouble. The circuit can carry an alarm signal in spite of and overriding a supervisory signal.