資料來源 : Free On-Line Dictionary of Computing

Primary Rate Interface
     
        (PRI) A type of {ISDN} connection.  In North America and
        Japan, this consists of 24 channels, usually divided into 23 B
        channels and 1 D channel, and runs over the same physical
        interface as {T1}.  Elsewhere the PRI has 31 user channels,
        usually divided into 30 B channels and 1 D channel and is
        based on the {E1} interface.
     
        PRI is typically used for connections such as one between a
        PBX (private branch exchange, a telephone exchange operated by
        the customer of a telephone company) and a CO (central office,
        of the telephone company) or IXC (inter exchange carrier, a
        long distance telephone company).
     
        (1995-01-18)