Valve position back to the hearing APL-411N passive contact rotary switch is dangerous situations provide a compact high-performance security products, is compact and beautiful, durable, valve status as a field test a meter, compact design, but also with more Item proof requirements, is a strong product market competition flameproof housing in line with EEx, IECEx, ATEX, dust proof (DIPA21 TA, T6) standard ...... ALS-500 Series Explosion valve position indicator is dangerous situations provides a compact high-performance security products, is compact and beautiful, durable, housing in line with E Ex, IECEx, ATEX, dust proof (DIPA21 TA, T6) standards. Features: 1-dimensional visual indicator, high-contrast color design, the whole point of view the valve position. 2. Meet the NAMUR standard, to maximize compatibility. 3. The anti-off screws, bolts removably attached to the cover when not fall off. 4. Ambient temperature: -25 ~ 85 ℃, the lowest reach -40 ℃, protection class: IP67. 5. The die-cast aluminum housing, anti-corrosion, polyester coating. 6. Double Connection: Dual 3/4 "NPT interface (with G1 / 2", 1 / 2NPT, G3 / 4 ", M20 * 1.5 available) 7. multiple contact terminal blocks, eight standard contacts. (there are multiple terminals to choose from) 8. spring loaded cam, tool to debug. 9. One of the smallest explosion-proof valve position switch for domestic type.