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 (氧化鋁)sensing shell and fine silver contacts which are hermetically sealed to ensure reliable operation. Electrical Rating (額定電功率)6-28 VDC, 1 amp. (all models) 上海朗飛自動化工程有限公司