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From: JOE@oregon.uoregon.edu
Newsgroups: comp.dcom.telecom
Subject: References/Fixes Needed For "Slippage" on Dialins
Message-ID: <12698@accuvax.nwu.edu>
Date: 27 Sep 90 16:44:53 GMT
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X-Telecom-Digest: Volume 10, Issue 687, Message 1 of 9


We've been experiencing a severe problem with noise on our dialins
which began, coincidentally, immediately after we got a new in-house
phone system here at the University of Oregon.  :-)

In talking with an E.E. friend and describing the symptoms (phantom
curly right braces and other characters typed "player-piano" style
with no keyboard assistance from the user required!), he suggested
that we are experiencing "slippage."

Because we run full-duplex, we've been able to determine that
sometimes the noise is introduced "inbound" (i.e., the phantom
characters appearing on the user's screen are also seen by the system
they've dialed into), while other times the noise is introduced
"outbound" only (i.e., the phantom characters appear on the user's
screen, but are never received by the remote minicomputer -- the
garbage disappears when the user forces a screen refresh).

The phenomena is stochastic, and apparently uncorrelated with anything
else we've been able to monitor (weather, system load, time of day,
type of modem user has, modem speed, particular modem dialed-in-to,
etc.).

Since this is driving our users crazy, we'd really like to resolve
this problem.

Can anyone provide me with a citation to some technical references on
slippage?  Has anyone come up with a fix for this sort of problem?
(I'd love to hear, "Well, if you just put an xxpF filter capacitor on
each of the modem lines...")

Thank you,

Joe St Sauver (JOE@OREGON.UOREGON.EDU or JOE@OREGON)
Statistical Programmer and Consultant
University of Oregon Computing Center