off the load current. There is photocoupler to isolate the input and output, no movable contact parts. It comes with the features of reliable, fast switch, noiseless, long life, compact, no spark, corrosion resistant, explosion-proof, antivibration and so on. It is widely applied in computer external connect device, constant heating equipment; numerical control machines, remote control systems, industrial automation equipment; signal lamps, traffic lights, stage lighting control equipment; instruments, medical equipment, photocopiers, photo printing, rubber and plastic machinery , automatic washing machine and many other fields where need the explosion-proof, anti-temperature, corrosion resistant. It becomes the ideal replacements of relay (EMR) family.