资料来源 : Free On-Line Dictionary of Computing

physical layer
     
         Layer one, the lowest layer, in the {OSI} seven
        layer model, concerning electrical and mechanical connections
        to the network.  The physical layer is used by the {data link
        layer}.  Example physical layer {protocols} are {CSMA/CD},
        {token ring} and bus.
     
        (1994-12-23)