Abstract: A duct mountable smoke detector includes a smoke sensor, an alarm indicating output relay, and an air flow control relay. In the presence of an alarm condition, the alarm indicating relay is energized thereby producing an alarm indicating signal. The air flow control relay is also energized thereupon changing an operative state of the respective air flow control element. Finally, a signal is coupled to an input/output interconnect port and, via an interconnect link, to other detectors coupled to the link. Other detectors coupled to the link which receive an alarm indicating interconnect signal energize the respective air flow control relays thereby changing operative state of the respective air flow control devices. The other detectors do not enter an alarm state. This allows for easy determination of the detector that initiated the alarm.

Abstract: A detector tamper/trouble delay circuit incorporates a sensor which senses the presence or absence of a cover for the detector. When the cover is removed, the sensor triggers a delay element preset for predetermined time interval. If the cover is replaced during the time interval, no trouble or fault indicator is generated. If the cover remains off the detector for the entire time interval, a trouble or fault indicator will be generated. The indicator can be used by an alarm system control element or a stand alone trouble or fault indicator for producing a humanly perceptible representation of the existence of the fault or trouble condition.