V.23

from The Free On-line Dictionary of Computing (8 July 2008)

V.23

   <protocol, standard> An {ITU-T} {modem} {protocol} which
   allowed {half-duplex} (unidirectional) data transmission at
   1200 bits per second with a 75 {bps} {back channel} and {fall
   back} to 600/75 bps.  This was the main standard used for
   {British Telecom}'s {Prestel} service.

   (2004-07-26)