IBM 2260 acoustic delay line

Christian Gauger-Cosgrove captainkirk359 at
Sat Dec 12 21:35:30 CST 2015

On 12 December 2015 at 22:13, Eric Christopherson
<echristopherson at> wrote:
> 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?
The delay lines were only within the 2848 control unit. From the
descriptions by others on the list, the 2260 displays were completely
dumb, and would display whatever was sent to them if I'm reading
things correctly.

> 2. I would think that the wave travelling along the delay line would
> weaken over time. How was it refreshed?
Once the signal reached the end of the delay line it was sensed,
regenerated and put back into the delay line, while also being
converted to scanlines to be sent to the 2260. Similar to the mercury
delay line memories of older machines like the UNIVAC, or EDSAC.
Though the 2848's delay lines were wire based not long mercury tanks.

> 3. What kind of speed could be acheived, and did this depend on the
> number of connected terminals?
You can most likely find that information in a manual. I think that
the A27-2700 manual will have it, located on BitSavers, of course:

Not an expert, just someone with some itnerest in it.

Christian M. Gauger-Cosgrove
Contact information available upon request.

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