Trailblazer and 3B1 uucp

[Kevin O'Gorman]

In article <169 at conrad.UUCP> sac at conrad.UUCP (Steven A. Conrad) writes:
>I have seen some discussion in the past about incompatabilities between
>the UnixPC modem and the Trailblazer.  I have not paid much attention
>since I did not ever plan on owning a Trailblazer, but now a friend
>has obtained one and I am having difficulty either getting a carrier
>or maintaining one once logged in.
>
>Could someone summarize the problem and any fixes if they exist?
>Thanks.

I'll give a try.  This is from memory, so don't bark at me if I miss
something.

There are basically three things that I have found one has to watch out for.

1) Since the UNIX PC timeouts are about 40 seconds, and not easy to change,
   you will probably want to have your friend set the modem's S92=1
   when he's waiting for a call.  However, see point 2.

2) This makes absolutely no sense, but you will have loads of trouble
   establishing carrier when the 'blazer calls you unless it has S92=0.
   I have had 'blazer folk deny this up and down, but none of them were
   the ones who actually tried it with me when I was debugging this
   problem.  Try it, and you'll be a believer.

3) You will not be able to communicate with the 'blazer when it is running
   its serial interface locked at a higher speed than 1200 baud (i.e. when
   it's running with S66=1 and a high interface speed).  Your friend may
   need to get one of the getty replacements that change the interface speed
   to match the communications rate.  The problem has been explained to me
   as being due to the 'blazer shaving the stop bit down below a full bits'
   duration, and the UNIX PC phone chip discarding characters that don't
   have a full stop bit.  This happens when the blazer internal buffer starts
   to get full, so it won't happen on short messages.

In other respects, the 'blazer manuals give adequate information for setting
up to communicate with the UNIX PC.