Abstract: An exit guiding system comprising detectors of changes in ambient condition due to a fire, a guiding device positioned near each fire exit or exit access, instruction means controlling operation or non-operation of each guiding device based upon signal levels from said detectors, operation of each guiding device being initiated when any detector outputs a signal indicating a dangerous condition, operation of individual guiding devices being suspended when ambient conditions local to said guiding device are dangerous, except the guiding device continuing operation when local conditions inside a door are dangerous but local conditions outside the same door are acceptable.

Abstract: A fire detector and a fire alarm system wherein a plurality of fire detectors are connected across a pair of lines leading to a signal station and which is capable of detecting, at the signal station, removal of a detector head or heads from an associated socket or sockets of any one or more detectors and yet capable of keeping the succeeding fire detectors operative to send a possible fire alarm signal even after removal of the head or heads. Each of said fire detectors comprises a means for disconnecting the line connected therethrough to the succeeding detector, temporarily in the course of removal of the detector head or heads from the associated socket or sockets or periodically after the detector or detectors has or have been removed from the associated socket or sockets. The signal station comprises a means for detecting the temporary or periodical disconnection of the line.

Abstract: A fire alarm system having a plurality of ceiling fixtures containing ionization smoke detectors which are located in regions of a building to be protected. Each smoke detector is connected to a common fire alarm signal receiver for sounding an audible alarm as well as a visual alarm in response to a fire alarm signal therefrom. Each ionization smoke detector is also provided with an ionization ambient atmosphere auxiliary co-detector for producing an auxiliary signal which is responsive to the environmental conditions of the detector in situ. The ambient atmosphere detector comprises an internal circuit having female terminals of a receptacle mounted in the wall of the corresponding fixture, and an external circuit having male terminals of a plug adapted to mate with the corresponding female terminals of such receptacle.