1.intrinsic safety telephone, with explosion-proof and safety certificate, 2.best ... not only used underground ,but also hard places with high temperature, high moisture, strong pollution;2 ... ) The material of cover is static-free, with features of waterproof, dustproof, anticorrosion and the ... 25°C);3) atmospheric pressure: 80kPa~106kPa;4) noise: ≤75dB;5) the place with explosive mixture, but without ...