Source : Free On-Line Dictionary of Computing

data channel
     
         A channel (on a {BRI} or {PRI} line) used to
        carry control information, to set up connections on the
        associated {bearer channels}.  The name wasn't too bad back
        when users were sending voice (not data) over the {bearer
        channels}, but in 1997 it's quite a misnomer.
     
        (1997-03-10)