heat detector,heat alarm 1)2 or 4 wire models 2) Fixed temperature and rate of rise 3) UL521, EN54-5 approved Marine Heat detector:12V D.C. or 24V D.C,48V dc; Power-off reset;Alarm indication: red LED onTemperature trip point: 57±3 degrees centigradeAlarm output : Relay output N.C. / N.O. optional2-wire, 4-wire for choice Fire Fighting Marine Heat Detector