[vcf-midatlantic] EAI TR20 analog computer exhibit

Herb Johnson hjohnson at retrotechnology.info
Fri Nov 18 10:53:08 EST 2016

SVCatITC [Bill Inderrieden] posted:

 >> I need analog math problems to be submitted, so that when the
 >> TR20 is restored, we'll have simulations to run on the computer.
 >> I'll make a list of what computational modules we have so you
 >> know what to work with, i.e.  integrators, DFG's, summers, etc.
 >> The plan is to have an XY  recorder and XY scope for results output.

Bill and all: I've taken the liberty to post  a reply under a proper 
subject line that's relevant to the thread. Not "digest question blah 
blah" which is irrelevant and will be impractical to search back for in 
the future. I really encourage people who post, to use relevant subject 
lines, but this is up to the Moderator to enforce, (except when he 

Bill, I worked with EIA analog computers long ago, and I'm an old 
electrical engineer. So it's good to see this EIA TR20 will be restored 
and demonstrated. But very few people in the VCFed list, have any 
experience with analog computing or with differential equations. Fewer 
visitors will know this stuff.

The classic demo of these sorts of systems, is some kind of "bouncing 
ball" display. Everyone has seen a ball bounce, so it's familiar. There 
ought to be enough integrators to make a damped oscillator. Since you 
want a chart recorder output, the frequencies will be sub-audio.

But you might allow for a speed-up at audio rates, so an oscilloscope 
and speaker can demonstrate operation, without requiring the chart 
recorder and using up paper and ink - all points of failure, weeks and 
months later.

  If it were my choice, I'd go "audio" so it's easier for the docents to 
demonstrate the unit and avoid problems with chart recorders.

That's my considerations. Something simple, familiar, and convenient to 
demonstrate when you aren't there. The amazing thing will be that it 
works, and has been preserved. We can run real programs, another day.

Herb Johnson

Herbert R. Johnson,  New Jersey USA
http://www.retrotechnology.com OR .net

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