IBM 2260 acoustic delay line

dwight dkelvey at
Sat Dec 12 21:41:53 CST 2015

From: cctalk <cctalk-bounces at> on behalf of Eric Christopherson <echristopherson at>
Sent: Saturday, December 12, 2015 7:13 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: IBM 2260 acoustic delay line

On Sat, Dec 12, 2015, Jon Elson wrote (in the big top posting thread):
> On 12/12/2015 07:22 AM, Mike wrote:
> >The one question I do have for the older gentlemen on here is what in the
> >world did the computers without a screen to look at do? Now I know about
> >the tape, cassette tape's and even the paper with the hole punches in them
> >but what kind of applications were they use for? Mathematics or? ? ?
> Later they got some
> IBM 2260's, which were Zenith 9" TV sets and a keyboard connected to an
> interface box in the machine room.  Very primitive, but very interactive,
> great for quick program editing and submission.

I'm reading about those terminals and find it just fascinating how they
used acoustic delay line memory to remember the pixels. But I have lots
of questions:

1. Did the cables connecting the 2260s to the display controller
actually contain the delay lines themselves, over the whole length; or
were the delay lines just inside the controller and then some electronic
signal was sent out to the terminals?

2. I would think that the wave travelling along the delay line would
weaken over time. How was it refreshed?

3. What kind of speed could be acheived, and did this depend on the
number of connected terminals?

        Eric Christopherson

I would assume it makes no sense to have it in the cable. It is acoustic not electronic.
Typically it would be a loop. Data and possibly clock goes in one end. At the other
end would be a preamp and recovery circuit. It would then be gated with 
possible new updated data and sent down the delay line again.
Tinker Dwight

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