Analogue Systems

Analogue systems use a graded system of detection. Conventional fire detectors give a “fire” response or “no fire” response, without providing any further information such as how much smoke there is. Analogue systems can measure and relay such information through the use of sensors instead of point detectors. The sensors do not actually make the “fire”/“no fire”: they send an analogue signal to the control and indicating equipment which is proportional to the sensed phenomenon. This signal can then be processed to determine the level of heat or smoke at the sensor and a decision can be made about whether the signal indicates an alarm condition.

Such a signal is used to give a pre-alarm signal to indicate a possible fire before a full alarm is sounded. It can also be used for system maintenance. For example, a smoke detector located in a dirty environment may become over-sensitised over time. The analogue system, with its increase in sensitivity, may be used for monitoring and maintenance warnings can be given.