Source : Free On-Line Dictionary of Computing

Basic Rate Interface
     
         (BRI, 2B+D, 2B1D) An {Integrated Services
        Digital Network} channel consisting of two 64 {kbps} "bearer"
        (B) channels and one 16 kbps "delta" (D) channel, giving a
        total data rate of 144 kbps.  The B channels are used for
        voice or user data, and the D channel is used for control and
        signalling and/or {X.25} {packet} networking.  BRI is the kind
        of ISDN interface most likely to be found in residential
        service.
     
        (2002-01-13)