The Free On-line Dictionary of Computing (30 December 2018):

V.34
V.FAST

    An ITU-T standard modem serial line
   protocol using symbol rates of 2400, 2743, 2800, 3000,
   >3200 and 3429 and up to 28800 bits per second.

   The official V.34 draft recommendation was titled:

      Modem operating at data signalling rates of up to 28 800
      bit/s for use on the general switched telephone network and
      on leased point-to-point 2-wire telephone-type circuits.

   During the lengthy process of approval by ITU-T, many
   manufacturers released 28.8 kbps modems described as "V.FAST".
   The V.34 recommendation was ratified by ITU-T on 20
   September 1994.  Rockwell and US Robotics both have seats
   on the ITU-T, and have both released chip set/BIOS
   combinations that they feel will meet V.34.  V.34 modems will
   also support V.FC if the manufacturer currently supports
   V.FC (e.g. Rockwell).  Some (all?) V.34 modems will also
   support line probing.

   ITU document
   (http://itu.int/itudoc/itu-t/rec/v/v34_25302.html).

   (1998-07-03)