> On Jun 26, 2020, at 1:46 PM, Tom Gardner <t.gard...@computer.org> wrote:
>
> Paul
>
> Thanks, I had found this ad a while ago but thought it was ¼-inch. Upon
> careful reading all the notes I found, "Errors per roll based on recording 7
> tracks on rolls ½" x 2500'. "
>
> It looks like 3M may have called their computer tapes "Instrumentation" tape
> until the late 60s
>
> Tom
"Instrumentation tape" sounds like a reference to instrumentation recorders,
which were devices used to record N channels of analog data. Typically this
was done by FM-modulating that data for the actual recording process. I've
seen references to heads for such machines in widths from 1/4 inch to 2 inches
depending on the number of channels needed. I believe instrumentation tape was
usually supplied on reels that look like professional audio tape reels -- metal
flanged reels with hubs somewhat larger than a standard computer tape hub, with
3 small notches.
Some early computers used tape like that for data recording; for example, the
Electrologica X1 used 1/2 inch instrumentation tape reels, recording data at
400 DPI (NRZI I think) in 10 (!) tracks. Those were vaguely like DECtape --
random access rewritable blocks -- but with variable rather than fixed length
blocks.
Recovering data from such reels is an interesting problem today.
paul
