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SCO Unix Serial Communications and UUCP

This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.

Why can't I get my dialin modem to work above 9600 baud?

This is an ancient post with no relevance to modern systems.

Because you need the modem speed in /etc/inittab to match the DTE rate that the modem is set for. If the DTE rate is fixed, the modem can connect with another modem at any speed. See /Unixart/hispeed.htmli for a full description of how to do this, but the overall picture is this:

  • The tty device (lowercase version) should be owned by uucp.
  • You need AT LEAST a Direct entry in /usr/lib/uucp/Devices referencing that device.
  • You may optionally have an ACU entry referring to the Upper case version: if you do, put that BEFORE the Direct entry.
  • In either case, make sure the speed entry matches the speed you will use in inittab.
  • Enable the Uppercase version in /etc/inittab at a fixed baud: do not use a cycling baud rate.
  • cu to the lower case version at the speed desired and issue whatever command is required to force the DTE rate to that speed.



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