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  • 21/08/2020
    Tunnel emergency telephone extension structure, extension working environment

    I. Extension structure The height of the microphone and receiver from the ground is 145±10cm. Emergency telephone has weather-proof facilities. Tunnel emergency telephone extension adopts metal box with steel plate thickness of more than 1.5mm, and adopts hot zinc spraying technology for antirust treatment, with zinc spraying thickness of 0.04 ~ 0.06 mm. After putty… Continue reading Tunnel emergency telephone extension structure, extension working environment

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