FWIW this is an announcement of a 3M brochure from a 1957 Datamation:
Magnetic Tape for Instrumentation, an 8-page brochure, covers six types of "Scotch" brand instrumentation tapes for use in telemetering and airborne recording, machine tool control systems, computers, geophysical recording, and other instrumentation applications. Included are charts listing physical and magnetic properties of each of the precision tapes and a comparison chart summary of major factors in selecting a tape for a particular application. Minnesota Mining & Mfg. Co., 900 Bush St., St. Paul 6, Minn. Circle 113 on Reader Service Card Apparently 3M “Instrumentation tapes” can be used for “computers” AFAIK 3M early “Instrumentation tape” types include Type 148/149 and Type 480/481 but both were announced after the 1957 brochure mentioned above It looks like all 3M “Type” tapes of this early era were available in a variety of widths, from ¼-inch to 2 inches -----Original Message----- From: Paul Koning [mailto:paulkon...@comcast.net] Sent: Friday, June 26, 2020 11:44 AM To: Tom Gardner Cc: cctalk@classiccmp.org Subject: Re: Early 3M Computer Tape Type Numbers > On Jun 26, 2020, at 1:46 PM, Tom Gardner < <mailto:t.gard...@computer.org> > t.gard...@computer.org> wrote: > > Paul > > Thanks, I had found this ad a while ago but thought it was �-inch. Upon > careful reading all the notes I found, "Errors per roll based on recording 7 > tracks on rolls �" 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
