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Using MultiTech Modems on Digi Ports in Unix

 This guide demonstrates configuration of many MultiTech Modems for use in a dialin application in a Unix-type environment:

1. DIP Switches If the Modem has DIP switches, set them to the async default position.

2. The command sequence for the modem should be:

?	at&w1z				-- reset modem to factory defaults 
					   and read DIP switches if present
	at$sbs0=1&w 	-- locks DTE speed at port speed
					   and stores to NVRAM

3. Follow the instructions in the Modem config FAQ for the particular Operating System.

4. Port should be set for rts and cts flow control. In SCO UNIX:

	ditty rtspace ctspace -ixon -ixoff -ixany /dev/ttyA01

(This can be put in the userdef file.)

Other Unix versions are similar. The correct syntax for this command in each Operating System is demonstrated in the appropriate Modem FAQ. Consult with tech support for further assistance if needed.

  • To verify DTE port speed, use the command
    and look for the $SB setting
    will show the S registers for confirming S0=1


  • Altpin needs to be configured correctly. (On for use with 8 wire cable, off for use with 10 wire cable). The modem may initially work with altpin set incorrectly but can fail if the remote site disconnects abnormally.


  • Some 14.4+ Modems will not work reliably if set for speeds below 38400, set modems for this speed and they will rate adapt to match remote site and line limitations.
Last updated: Aug 23, 2017

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