have detected a hazardous condition can each disable device 40 1 based on a local sensed condition similarly detectors 50 5 50 6 which are coupled to the e d port of path indicating device 40 2 can disable the audible or visual output therefrom in the event of a hazardous condition on or in the vicinity of the pathway e in the immediate area of output device 40 2 it will also be understood that the devices 50 1 50 4 could also be coupled to the e d port of output device 40 2 without departing from the spirit and scope of the present invention similarly output devices 40 3 40 n have e d ports coupled to a plurality of detectors 50 7 50 m located along or adjacent to exit path e detectors 50 1 50 m are located in the vicinity of the exit itself any of the detectors 50 7 50 m can disable any of the respective output indicating devices 40 3 40 n as it will be understood by those skilled in the art one type of enable disable port can have terminals which accept normally open and or normally closed contacts a change of state at one of these terminals normally open contacts closing or normally closed contacts opening causes the respective output indicating device to become disabled for example normally open or normally closed contacts from the respective detectors can be directly connected to this form of e d input port in the case of normally open contacts the detectors.