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Chapter 6 – Fax Class 1 and Class 1.0 Commands
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 87
Fax Mode Selection
Fax Class 1 and Fax Class 1.0 commands are identified in Table 6-1. Fax Class 1.0 includes all Fax
Class 1 commands
Table 6-1. Fax Class 1 and Fax Class 1.0 Commands
Command/Parameter Function Applicable in
Fax Class 1
Applicable in
Fax Class 1.0
+FCLASS=<class> Select, read or test service class X X
+FAA=<value> Auto answer enable - X
+FAE=<value> Auto answer enable X X
+FTS=<time> Stop transmission and pause X X
+FRS=<time> Wait for silence X X
+FTM=<mod> Transmit data with <mod> carrier X X
+FRM=<mod> Receive data with <mod> carrier X X
+FTH=<mod> Transmit HDLC data with <mod> carrier X X
+FRH=<mod> Receive HDLC data with <mod> carrier X X
+FAR=<off/on> Adaptive reception control - X
+FCL=<time> Carrier loss timeout - X
+FDD=<value> Double escape character replacement control - X
+FIT=<time>, <action> DTE inactivity timeout - X
+FPR=<rate> Fixed DTE Rate - X
+FMI? Report manufacturer ID - X
+FMM? Report model ID - X
+FMR? Report revision ID - X
+FLO Flow Control - X
&K Local DTE-modem flow control (see Call
Control Section)
XX
AAnswer XX
D<string> Dial X X
H Hangup (see Call Control Section) X X
X stands for Applicable. - stands for Not Applicable.
Fax Origination
Origination of fax calls is made using the ATD command. Upon completion of the dial function, a calling
tone at 1100 Hz is transmitted, with a cadence of 0.5 seconds on and 3 seconds off. The modem
automatically enters mode +FRH=3 and sends the CONNECT message to the DTE when FSK flags are
detected from the remote.
Fax Answering
Answering of fax calls is identical to answering of data calls with the exception that the modem enters the
fax handshaking mode instead of the data handshaking mode after going off-hook. If +FAE=0, the
modem, after sending answer tone, automatically enters fax mode (+FTH=3), sends the CONNECT
message to the DTE, and starts sending FSK flags. If +FAE=1, the modem determines whether the caller
is a data modem or fax modem and sends the DATA or FAX result code, respectively, to the DTE.
Fax Control Transmission
Fax control transmission is initiated by the +FTH=<mod> command. After this command is issued, the
modem generates the CONNECT message and transmits carrier in the modulation scheme specified by
the parameter n. The modem then transmits HDLC flags for a minimum of 1 second. The modem
continues to transmit the HDLC flags until it receives a character from the DTE.
When characters are received from the DTE, the modem adds start and end flags, performs zero-bit
insertion, generates FCS, and deletes <DLE><chr> character pairs before transmitting the characters to
the remote fax machine. Each <DLE><DLE> sequence is transmitted as a single <DLE>. <DLE><ETX>
is considered as the end of frame marker and is not transmitted. All data received from the DTE after