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From: jeffj@sfsup.UUCP
Newsgroups: comp.misc
Subject: re:IBM 1130 Emergency Pull switch
Message-ID: <1092@sfsup.UUCP>
Date: Fri, 6-Feb-87 18:00:48 EST
Article-I.D.: sfsup.1092
Posted: Fri Feb  6 18:00:48 1987
Date-Received: Sun, 8-Feb-87 05:30:21 EST
Organization: AT&T-IS, Summit N.J. USA
Lines: 52

I never pulled the 'emergency pull' switch for fear of crashing the disks.
As it turns out, he heads are loaded by a solenoid, so turning the power
off raises the heads.  I'm not sure if they'd retract properly
when powering up again (to load properly on the outer tracks).

Professor Costello (of The Cooper Union), however, always wondered what happens,
so he pulled it.  The power went off to everything.
You see, the switch turns off the main power relay,
and turns everything off without regard to the sequencing.
There is a collar on the knob shaft, behind the panel.
There is a spring resting on the collar, like this


side view:	      panel
                        |
                        |    [[]]
                []           [[]]
 switch ========[]===========[[]]
                []           [[]]
                 /      |    [[]]
                /
               /
	     spring

The spring snaps behind the collar, preventing you from pushing
the button back in.
I know because I have the button and panel piece right here.
(Yup, I have pieces of the 1130 all over my home and office).
This is the same on the system 3.
Just a poke with a screwdriver gets it reset.
The spring can be bent to never interfere again.

In <3378@milano.UUCP>,  John Fehr says that "after 15 years, the plastic becomes
a bit brittle".  I guess that the knobs were changed to plastic at some time.
Mine is all metal.  The Amdahl's are metal too.

In <706@argus.UUCP>, Art Marriott says that the IBM CE had to reset the switch.
Yup, that's the function of the spring and collar.  I guess that the power
sequencing was important enough that maybe things would lock up or get
damaged (like the disks?).  Or it was a gimmick to get extra service
calls (if you're desperate enough to pull the Emergency Off switch
instead of just turning it off, you deserve to be punished).

	Jeffrey 'paper based lifeform' Skot
	{ihnp4 | allegra | cbosgd} attunix ! jeffj


P.S.  I had two of the hole punches used for the 1132 printer's
carriage control tape (remember the 12 channel tapes?).
I remember places like INMAC charging around $200 for them.
After nobody wanted to buy them, I donated them to The Smithsonian.
They truly are "The Nation's Attic".