所有302系列的探测器都是常开的系统，有135华氏度（57摄氏度）和194华氏度（90摄氏度）两种定温度等级。

All 302 Series Detectors are normally open devices and are available in either 135°F (57°C) or 194°F (90°C) ratings. Each unit is constructed with a high expansion .040 anodized aluminum （氧化铝）sensing shell and fine silver contacts which are hermetically sealed to ensure reliable operation. Electrical Rating （额定电功率）6-28 VDC, 1 amp. (all models)