IBM 2260 acoustic delay line

William Donzelli wdonzelli at
Sat Dec 12 21:37:14 CST 2015

The IBM 2848, the control unit for the 2260 terminals, contained
mercury (!) delay line for the video memory. There may have been some
compensation for the transmission to the terminal, but I have have not
seen the technical details - I think it was not a concern, probably.

Line loss is really not a problem. It might have been if the lines
were miles long, but in typical installations, that was not anywhere
near a problem.

As for speed - not an issue for basically baseband video.


On Sat, Dec 12, 2015 at 10:13 PM, Eric Christopherson
<echristopherson at> wrote:
> 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? ? ?
> [snip]
>> 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

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