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From: chrise@ihlpa.UUCP (Chris Edmonds)
Newsgroups: net.rumor
Subject: Re: apocryphal story about ESS crashes - can someone confirm it?
Message-ID: <170@ihlpa.UUCP>
Date: Fri, 29-Mar-85 13:38:31 EST
Article-I.D.: ihlpa.170
Posted: Fri Mar 29 13:38:31 1985
Date-Received: Sat, 30-Mar-85 01:29:20 EST
References: <3957@Shasta.ARPA>, <63@decvax.UUCP> <5363@utzoo.UUCP>
Organization: AT&T Bell Laboratories
Lines: 35

> The apocryphal story I heard had to do with the light from the sun shining
> through a glass window and hitting all the end of tape sensors in a rack
> etc., etc.,

Yes this really happened (sort-of) with all the caveats previously 
mentioned in other responses (i.e., No crash, just moderate confusion
of the system which was easily resotered, no loss of service). I was
personally involved in this one and hand built the "little hood" which
was installed on ->ONE<- machine.

The situation was like this... In the late 70's WE was installed 2BESS
machines all over creation and its processor was known as the 3A Processor.
This processor was used in a number of other installations. I owned the
current engineering responsibility for the peripheral frame for this machine.
The system boot device was (and still is) a 3M like tape cartridge drive
physically mounted such that the optical sensors looked straight out the
front of the machine.  Normally these were not affected by visible light
as they are tuned to look for infared (LEDs with filters).

One of the installations was on the zillionth floor of the NW Bell
building in Seattle. It just so happened that this building had lotsa
windows (unusual for a Bell structure) and the processor was installed 
facing one on the west side of the building.  I'm sure you can guess the
rest.

It was summer so it took a little longer to figure it out.  Some evenings 
after the installers went home the tape would run off reel.  It finally
dawned :-) on us that it happened at sundown on sunny evenings.  The sun
was shining directly into the housing and swamping the sensor.  Since it
was edge sensitive the sensor never saw the BOT hole go away and never ramped
the motor down.  The result was a specially fabricated opaque cover which
had to be manually lifted to install the tape cartridge.  As far as I know
its still there.

Chris Edmonds @ Bell Labs, Naperville IL