Ericsson ZAT 19.2 Operation Manual page 300

Connecting up in V.32 bis
During a V.32 bis handshake sequence, both modems try to
learn as much as possible about the current telephone channel,
and also some negotiating between the modems take place.
Below are listed up some of the key items.
Determination of round trip delay, for the echo canceler.
Training of the adaptive equalizer.
Negotiate about the bit rate, and if TCM shall be used
Synchronizing the receivers.
The figure below show the handshake sequence.
Call mode modem
jaa [CC | s| 5 TRN| Rate signal R2 | E| B1 | Data
i! Note mt fos
second
107 __JPaciamp .
pros
angcical_acj{_[ sl Iran[ ri] [is] TRN[ R3] Ef 81] Data|
te} fol bello Se
V.25 2128T 64Tz22T16T 256T -1280T 256T £1280T aT
107 __[ unctamp 1
109
Answer mode modem
AC Signal states ACAC. AC for an even number of symbol intervals T:
similarly with CA,AA and CC.
MT, NT Round-irip delays observed from answer and call modems
respectively, including 64T+2T modem turn round delay.
S,S Signal states ABAB.. AB, CDCD..CD
TRN Scrambled ones at 4800 bit/s with dibits encoded direclly to states
A.B,C and D
Rt, R2, R3 Each a repeated 16-bit rate sequence at 4800 bil's scrambled
and different encoded as in Table 1/V 32
B1 Binary ones scrambled and encoded as for the subsequent
transmission of data
"The inclusion of a special echo canceler training
sequence at this point is optional
1 5-1 2 LZTR104006 R1.00
Zat14.4/14.4-7 and 19.2/19.2-7