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Chapter 3 – Fax Class 2 Commands
Multi-Tech Systems, Inc. SocketModem MT5634SMIxx Reference Guide (S000263C) 72
Parameter Commands
All Class 2 parameters can be read, written, and tested for the range of legal values by the modem.
The general syntax is described in the AT Command section of this Chapter.
T.30 Session Parameters
Group 3 fax devices negotiate session parameters in the DIS, DCS and DTC frames. The following
parameters are provided to condition the fax modem for the capabilities it will offer, and to report the
negotiated session settings.
The three primary T.30 session parameters are +FCC [FDCC], +FIS [FDIS] and +FCS [FDCS],
described in 2.5.1.1–2.5.1.3. These are compound parameters using values listed in Table 3.5. The
Figure below illustrates their relationships:
DTE Write
DTE Read
DTE Write
DTE Report
DTE Read
DTE Write
DTE Read
+FCC
DCE Capabilities
+FIS
DCE Negotiating
Position
+FCS Negotiated
Session Parameters
On send,
determine
DCS in
fax DCE
Cold
Start
Write
+FDCC
End of
Session
Cold
Start
End of
Session
0,0,0,0,0,0,0,0
Remote DCS on receive
DIS/DTC
from remote
station
DCS if send
DIS/DTC if receive
Virtual DIS
on send
T.30 session parameters
Modem Capabilities Parameters
Class 2.1 +FCC=
Write Syntax: +FCC=VR,BR,WD,LN,DF,EC,BF,ST,JP
Values: See Table 3.5
Default: 1,5,0,2,0,0,0,0
+FCC allows the host to sense and constrain the capabilities of the facsimile modem,
from the choices defined in ITU-T T.30. When +FCC is modified by the host, the
modem will copy +FCC into +FIS.
Note: The Multi-Tech implementation does not include the T.32 subparameter WD 3
and 4 values or the EC 2 and 3 values; also, for subparameter BF only the 00 value
is implemented.
Class 2 +FDCC=
Write Syntax: +FCC=VR,BR,WD,LN,DF,EC,BF,ST
Values: See Table 3.5.
Default: 1,5,0,2,0,0,0,0
The Class 2 parameter is essentially the same as the Class 2.1 parameter except
that it lacks the JP subparameter, and the modem copies +FDCC into +FDIS.