MODE OF DETECTION
Rate-of-Rise
Being the first stage of detection, the Detector senses the rate-of-rise of temperature around its zone of coverage. When the rate of temperature increase 6°C within 4 seconds, the detector instantly switches from its normally open circuit to close circuit to activate the fire alarm. At the same time, the light emitting diode (LED) is illuminated indicating its active mode. It will remain active until the ambient temperature reduces substantially enough to automatically reset it back to its open circuit mode (dual detection mode).

Under normal day temperature fluctuations, the detector remains in standby mode. The current consumption while in standby mode is nil, and changes to 1.5mA when the detector is activated.

Fixed Temperature
The fixed temperature method comes into action in cases of slow smouldering fire where the temperature does not increase at the rate that would trigger the rate-of-rise detection.

At any time when the temperature in the zone coverage reaches a predetermined point which is factory calibrated, a snap action mechanism switches the detector from its standby open circuit mode to close circuit mode permanently. Once this has taken place, the unit will not reset itself and the LED indicator will stay lighted. Replacement of the set is required.