[GreenKeys] [External] Re: 9 - level?

[Nick England]

And leave us not forget Colossus, reading paper tape at 5000 characters/sec
with the sprocket hole providing the strobe pulse. Using photomultiplier
tubes in 1944.
Tape speed 30 mph.

Nick England K4NYW
Chapel Hill NC
www.navy-radio.com

On Fri, Aug 28, 2026 at 5:40 PM Jones, Douglas W via GreenKeys <
greenkeys at mailman.qth.net> wrote:

> From: Harold Hallikainen via GreenKeys <greenkeys at mailman.qth.net> --
> Friday, August 28, 2026 3:55 PM
>
> On Fri, August 28, 2026 1:11 pm, David Wade via GreenKeys wrote:
> ? The feed hole detector was a strobe for the data since the hole is
> smaller than the data holes and centered on the data.
>
> Lots of high-speed photoelectric paper-tape readers worked that way.  I've
> got an old IOMEC reader that has a capstan and pinch roller to move the
> tape (very fast, no sprocket anywhere), an electromagnetic brake to stop it
> (on a dime) and 9 channels of photocells, the sprocket cell serving as
> strobe.  It shows its age because it uses a single incandescent bulb to
> illuminate all tape channels where a design from after about 1972 would
> have used one LED per channel.
>


>
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