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)



302-135- Interior, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50'
302-194 - Interior, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 

这款应该是室内使用 



302-ET-135 - All Weather, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50' 
302-All Weather, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 

这款是所有的环境使用



302-AW-135 - Moisture and Dust Proof, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 50' x 50' 
302-AW-194 - Moisture and Dust Proof, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 50' x 50' 

这款是防潮和防尘



302-EPM-135 - Explosion Proof Screw Base, Vertical Mounting Fixed Temperature 135°F Maximum Spacing - UL 40' x 40' 
302-EPM-194Explosion Proof Screw Base, Vertical Mounting Fixed Temperature 194°F Maximum Spacing - UL 40' x 40' 

这款是防爆的，也是最贵的价格差一倍多