Apparatus and method for detecting the occurrence of an alarm condition

Abstract

An alarm condition detection apparatus and method is embodied in the form of a combustion products detector for detecting fire. The detector generates a difference voltage signal proportional to the degree of combustion products in the atmosphere being monitored. The difference signal is employed to generate an alarm signal to indicate when the condition reaches an alarm state. The detector is adjustable to control the level of a reference voltage which in turn controls the difference signal voltage change needed to cause generation of an alarm signal. Thereby, detector sensitivity is set. The detector includes circuitry operable to generate in response to the difference signal a series of perceptible pulses having a pulse rate proportional to the magnitude of the difference signal. Thereby, with the condition normal, the pulse rate provides a perceptible indication of detector sensitivity. Further, the pulse rate change occurring as the condition approaches alarm state provides a perceptible indication of the approach. Additionally, the detector may be arranged so that a change in the difference signal to a predetermined trouble level causes a trouble signal to be generated to indicate low operating voltage, component failure, or improper sensitivity setting. Alarms may be included or associated with the detector for indicating occurrence of the alarm condition and/or to indicate trouble.