Specifications
    Chapter 2 – Fax Class1 Commands 
Multi-Tech Systems, Inc. SocketModem MT5600SMI/MT5656SMI Reference Guide (S000306B)  71 
Command:  +FDD  Double Escape Character Replacement 
Description:    This parameter conditions the use of the ˜DLE˜˜˜SUB˜ pair to encode 
consecutive <1/0 €<1/0 in data. This may be used to prevent unbound 
expansion of data that contains many <1/0 patterns. 
Defined Values:   <value> Decimal number corresponding to the selected option. For modem 
decode of <DLE><SUB>, the defined range are: 
    0 <DLE> <DLE> or discard (default and only) 
    1 <DLE> <DLE> (not supported) 
    For modem encoding of <1/0> <1/0>the defined values are: 
    0 <DLE> <DLE> <DLE> <DLE> (default and only) 
    1 <DLE> <SUB> (not supported) 
Reporting Current or Selected Values: 
 Command: +FDD? 
 Response: +FDD: <value> 
    Example: +FDD: 0 For the default setting. 
Reporting Supported Range of Parameter Values: 
 Command: +FDD=? 
    Response: +FDD: (<value> range) 
    Example: +FDD: (0) 
Command:  +FIT  DTE Inactivity Timeout 
Description:    This command specifies a DTE inactivity timeout value that allows the modem 
to break away from an unsuccessful connection attempt at any stage of a 
facsimile transfer. The DTE inactivity timer operates only while the modem is 
off-hook.  
Defined Values:   <time The <time parameter indicates the DTE inactivity timeout in seconds. 
The value of 0 indicates that timeout is disabled (default). The required 
timeout range is 1 to 255 seconds. The inactivity timer starts when the modem 
has taken some action that requires DTE response. If the DTE does respond, 
the modem resets the inactivity timer. Inactivity timer related events are listed 
in Table 2-3. 
    <action The <action parameter has two meanings. 
    0 Upon timeout, the modem will go on-hook, executing an implied ATH 
command; then reset to +FCLASS 0. 
    1 Upon timeout, the DCE will only go on-hook. 
Reporting Current or Selected Values: 
 Command: +FIT? 
    Response: +FIT: <time ,action 
    Example: +FIT: 0,0 For the default settings. 
Reporting Supported Range of Parameter Values: 
 Command: +FIT? 
    Response: +FIT: (<time> range), (<action> range) 
    Example: +FIT: (0-255),(0-1) 
Table 2-3. Inactivity Timer Start and Stop Events 
On-line state  Start timer event  Stop timer event 
Waiting for a command  modem sends final result code  DTE sends AT or “at” 
Waiting for transmit data  modem sends CONNECT after +FTM or 
+FTH command 
DTE sends data 
Waiting for transmit data  modem sends <XON or sets CTS ON  DTE sends data 
Waiting to deliver received data  modem sends <XOFF after +FRM or +FRH 
command 
DTE sends <XON 
Waiting to deliver received data  DTE sets V.24 Ckt 133 OFF after +FRM or 
+FRH command 
DTE sets V.24 Ckt 133 
ON 










