Model dcd, Ae3 hfp is a rate of rise heat detector with a 60 c fixed temperature element using a thermistor and linearising circuit to offer a accurate linear response heat detector. The dcd, Ae3 hfp works exceptionally well for use where medium ambient temperatures exist, Such as drying rooms or where smoke detectors are unsuitable therefore of the occurrence of steam or cooking fumes such as in a kitchen. The dcd, Ae3 hfp is aided by a selection of bases for different applications and these are supported on the vast number of conventional systems. A third terminal provides remote indicator output.