... ,shipping ,shipping port ,railway tunnel and other rough area.2 Feature2.1 Shell of the explosion-proof telephone made of ... steel keypad, which contact resistance below 30ohm,life cycle above 2 million,push force 160-200grams,defend grade is up to IP67 ... function with srore ,memory,dial (Each number up to 16 )2.7 Easy for install and operate3.Technical parameterDefend gradeIP67Ambient temperature ...