Abstract: A multistationed integrated life safety system in which each station will be situated at a diffferent location and have complete capabilities in terms of local fire protection, fire detection, control and/or monitoring and controlling the security of an area. Each station communicates with four adjacent stations so that when an event occurs at one station, that station is programmed to cause that information or that new status to be transmitted to each of the four adjacent stations. Thus, each station will be interconnected or networked to four other stations to provide multiple location control and annunciation so that each station may act independently.

Abstract: A radiation detector for use in hazardous locations, comprising an explosion proof housing with a viewing window and a detector element positioned inside the housing to receive radiation through the viewing window, and means within the housing to apply test radiation onto the external face of the viewing window directly. In one embodiment of the invention the viewing window is recessed in a housing cavity with a flared wall and the test radiation is applied from a housing portion that extends forwardly of the plane of the viewing window. In a preferred embodiment of the invention the housing is formed of front and rear portions which are rotatable in relation to each other, and the viewing window is mounted in a surface of the front portion which is inclined at a 45.degree. angle to the axis of rotation of the portions, and the rear portion has mounting means enabling mounting of the detector so that it can rotate about an axis disposed at a 45.degree.

Abstract: A detector circuit for detecting an unwanted ground coupled to either terminal of an ungrounded d.c. power supply. The circuit uses simple and economical components including four resistors, two diodes and a single voltage comparator. The resistors provide two voltage dividers whose midpoints are at different potentials. The two midpoints are coupled by the two diodes in series with the midpoint of the diodes grounded. A voltage comparator is coupled to the voltage divider midpoints. Any unwanted ground will shift the relative polarity of the voltage divider midpoints and alter the output signal of the voltage comparator.