SUMMARY L1-A and Annex

From: Steve Swaney (
Date: Fri Jan 07 1994 - 04:52:29 CST

Dear fellow admins,

This summary has been delayed until we could test solutions.

The problem:

Turning off an Annex (and many other brands) Terminal server which serves as
the console for approximately 32 Sun servers causes all the Suns connected to
the Annex to halt.

The winning answer was from Torsten Metzner,, who pointed
me to Hal Stern's excellent paper "", available ftp from : pub/sun/

The paper contains a circuit diagram which pointed us to solution. Using Hal's
diagram we contacted:

        NuData Inc.
        32 Fairview Avenue
        Little Silver, NJ 07739-9976
        Ron Sealy Engineering (908) 842-5757

Who sent us an A-D -> I/0 serial switch box they market to share one console
between 5 Suns. The switch box had the circuitry we needed to prevent the
"break" signal on disconnection of the terminal.

They are building this circuitry into a "gender-bender" sized connector that we
will insert between ttya on the sun and the cable to the Annex. While we do not
yet have the final product, we anticipate that it will work based on our
testing of the switch.

The cost of each gizmo in quantities of about 100 will be +-$80.

After installing the circuit all works normally. L1-A will still halt the
system, but disconnecting or powering off the Annex has no ill effect on the
Suns. This solution should work on all terminals and terminal servers which
exhibit this problem. For the worried - Wyse terminals do, vt-200 do not. Most
terminal servers do.

Several of the replies suggested kernel mods which would also solve the problem
in various ways. We elected to go with the hardware solution since the numerous
systems involved are administered by many different groups and hey - some
people never get the word.

Many thanks to:

Donald McLachlan (
Dan Stromberg - OAC-DCS (
Dave Twinam (
Tim White (
Richard Doty (
Jim Ahokas (csfb1!next8!ahokas@uunet.UU.NET)

Steve Swaney
1 (212) 902-4526 (desk)
1 (917) 859-4229 (cellular)

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