At calling time the sequence as described above with the
              FSK  type  modem is valid for the V22(bis).  The  called
              modem  reacts instead or after the answer sequence  with
              unscrambled binary '1's at 1200 bit/sec. and well in the
              upper channel (2400 Hz.  carrier).  This till it detects
              scrambled  '0'  or '1's in the lower channel  (1200  Hz.
              carrier).  The calling modem remains silent till it  for
              155 msec. detects unscrambled '1's in the upper channel,
              after  which it remains silent for 456  msec.  and  then
              transmit  unscrambled  double dibits 00 and  11,  if  in
              V22bis mode,  for 100 msec. followed by scrambled binary
              '1's  or  if in V22 mode it transmits  direct  scrambled
              binary '1's (*).  Here the distinction 1200/2400 baud is
              made by the calling modem.  The called modem reacts with
              scrambled '1's preceded,  if V22bis with the unscrambled
              double  dibit 00 and 11.  At the moment of detection  of
              the  double dibits,  the circuit CI/112 (pin 12) is  set
              true (indicating 2400 baud). In both cases the scrambled
              '1's are observed for 600 msec.  after which the circuit
              CF/109  (pin  8)  is set true.  If V22 (1200)  the  data
              transfer is started under control of CA/104 (pin 3).  In
              the V22bis mode (2400),  first scrambled binary '1's are
              send  form  both sides for 200 msec.  on  2400  bit/sec.
              mode.  Noted,  that till now all was transmitted on 1200
              bit/sec.  After this 200 msec.  also the V22bis mode  is
              ready for data transfer.
              I know it is confusing, but so it works. To make it more
              difficult,  the  (*)  mentioned in the text is true  for
              V22bis  and for V22 alternative A and B  only.  For  V22
              alternative  C,  for the '1's you have to read '0's.  As
              the  V22  norm is very confusing on  some  aspects,  one
              remark   has  to  be  made.   In  V22  (not  V22bis)   3
              alternatives  can be selected.  Alternative A and B  are
              compatible  with  V22bis,  but alternative  C  not.  The
              difference  is the scrambled binary '0's stead  '1's  of
              the  calling  modem.  So  the  real  difference  between
              alternatives  A/B and C is,  that alternative C includes
              the  possibility for mode V,  for  anisochronenous  data
              upto  300  bit/sec.  Which manufacturer tells  me  which
              alternative  as mentioned in V22 he serves.  Or has this
              to do with the Bell-212 norm.  Who can tell? Has this to
              do with the famous ATBn command in the HAYES-2400 modem?
              See above.

              Be  carefully  with these V22 and  Bell-212A  norms.  As
              explained   before  only  the  2400  baud  (V22bis)   is
              compatible. The 1200 sometimes works, but sometimes not.
              E.g.  I  had an USA RIXTON 212 modem,  not corrected for
              the European market. Also I had a Dutch designed (DATAD)
              V22(bis) V23 and V21 modem and an English (PACE) for the
              same  speeds.  The RIXTON works pretty most at the  time
              with  both the DATAD and  PACE modem.  But sometimes  it
              goes  wrong and the Eurpeans connects at 2400,  which is
              strange,  but true. With an original HAYES-1200 (with no
              ATBn)  command as the HAYES-2400 has,  nearly  the  same
              result. The two Europeans hardly are connectable at 1200
              baud  to each other.  This has in my opinion to do  with
              the  way of speed selection.  We try to come out of this
              struggle.