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US Robotics Modem Configuration in UNIX

 This guide demonstrates configuration of US Robotics Sportster and Courier modems for use in a dial-in application in a UNIX-type environment:
  1. DIP switches
    • Sportster modems should be set initially for
    • DIP switches 3,7, and 8 down (The rest UP)
      Switch 3 Down is display result codes
      Switch 7 Down is Load factory defaults
      Switch 8 Down is Smart Mode
    • Courier modems should be set initially for
    • DIP switches 3 and 8 ON (The rest OFF)
      Switch 3 On Display Result Codes
      Switch 8 On Enable AT Command Set
  2. the command sequence for the modem should be:
    	at&b1&w
    
    		&b1 -- fixed serial port rate
  3. Follow the instructions in the Modem config FAQ for the particular Operating System.
  4. Port should set for rts and cts flow control. In SCO Unix this is
    	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.

  5. Once the port is working properly, then change the following DIP switch to save NVRAM settings:
    • Sportster switch 7 should be flipped UP to use saved settings.
    • Courier switch 10 should be flipped ON to use saved settings.
Notes:
  • Switch 5 Up/Off is Auto Answer on first ring (or higher if specified in NVRAM with ATS0=# -- the default is S0=1). Thus ATS0 does not need to be set for most applications.

     

  • To verify DTE port speed, use the command
    ATI5
    the BAUD setting in TEMPLATE Y0 will reflect the current port speed.

     

  • 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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