<DLE><ETX>
OK
Dial and send CNG
Look for V.21
Detect flags
Answer
send CED, V.21
Send HDLC flags
Send NSF frame
AT+FRH=3
implied by dialing with
+FCLASS=1.0
AT+FRH=3
CONNECT
<CFI frame data>
<DLE><ETX>
OK
Detect flags
get CSI
get FCS
accept FCS
send CSI frame
check FCS Frame status OK
AT+FRH=3
CONNECT
<DIS frame data>
<DLE><ETX>
OK
Detect flags
get DIS
get FCS
accept FCS
send DIS frame
check FCS
DTE must detect final
frame bit to anticipate
loss of carrier
AT+FRH=3 NO CARRIER detect loss-of-carrier drop carrier
AT+FRH=3
<TSI frame data>
<DLE><ETX>
<DCS frame data>
<DLE><ETX>
CONNECT
CONNECT
OK
send V.21 carrier
send flags
send TSI frame
send FCS
send flags
send DCS frame
send FCS, flags
drop carrier
detect carrier
detect flags
get TSI frame
get DCS frame
Final frame bit clear tells
the modem to expect
another frame.
Final frame bit set tells the
modem not to expect
another frame
AT+FTS=8;
+FTM=96
<TCF data pattern>
<DLE><ETX>
CONNECT
OK
wait 80 ms
send V.29 carrier
send TCF data
drop carrier
detect carrier
get TCF data
AT+FRH=3
CONNECT
<CFR frame data>
<DLE><ETX>
