Abstract: An automatic fire detection system characterized by an extremely low incidence of false alarms utilizes two detection channels, one fed by an infrared (IR) detector and the other by an ultraviolet (UV) detector. Signal processing electronics in each channel produce a normalized output signal proportional to the power of incident IR and UV radiation within specific bandwidths. The system features a ratio detector that repeatedly forms a ratio of the normalized IR and UV inputs and compares the ratio to a known range of values for this ratio that are characteristic of a fire. A discriminator connected to the output of the ratio detector generates a fire alarm signal only if the majority of these ratio comparisons are fire-indicating. The system also includes a feedback loop in the IR processing channel that automatically adjusts the output of the channel to compensate for time-varying background IR radiation such as sunlight.

Abstract: An overtemperature detection cable for use with a fire alarm system, a fire extinguishing system or the like comprises a coaxial assembly of an inner spring wire conductor in a core of thermoplastic dielectric material within an electrically conductive outer sheath. In one embodiment, the spring wire is initially coiled in a three-dimensional helical configuration, is thereafter uncoiled to approximate a straight wire, and is then disposed within the outer sheath to reside in the thermoplastic dielectric core. In a second embodiment, a straight inner spring wire and its surrounding thermoplastic dielectric core reside within an outer sheath, and the assembled sheath, wire, and thermoplastic dielectric material are then bent or crimped to assume a two-dimensional sinusoidal configuration.