HP2748A papertape reader : connector ?

Bob wrote... documentation In system. No Kidding!? That's truely interesting. You have my curiosity up, I'd love to know what the deal is for my own future reference. I do have a lot of sales literature and marketing collateral for these systems, and all of them show the 2748B paper tape reader as using an 8-bit duplex register board. Hummmmmmm.... You know what - is it possible that the ones that use this "tape reader interface board" that you've seen are the 2748A reader and the B version uses the 8-bit duplex register board? All the literature and docs I have shows the 2748B, I have nothing that relates to the 2748A which is why I'm conjecturing this. One wouldn't think that HP would release a board with the same electrical specs as the 8-bit duplex board, so wouldn't you think the electronics in the reader would have to be different for the two boards? Most interesting... could you check and see if your reader is the A one that uses this board Bob? Or maybe show us a pinout of the old style reader interface vs. the new style? small I knew the first 21xx machine was already designed and put together by another company, and HP just absorbed the company. When they saw how sucessfull it was, they then came out with the other two. I was thinking this first one was the 2114, and the HP made ones were the 2115 and 2116. I stand humbly corrected - must be the 2116 that was absorbed and they made the other two. The 2100 did come later. Interesting tidbit - one of HP's largest users of the 2100 system was a company called "MeasureX". This company had it's own engineering staff and redesigned the 2100 to be a single cpu card. They sold this design back to HP and it became the 21MX line. The MX in 21MX stands for MeasureX. I got this directly from a phone call with the former VP of engineering of MeasureX, so I suspect it is accurate historically. I'm just wild guessing here, but is it possible that the 2100A that you got had the tape reader (old style) added later and wasn't actually sold that way from HP? The reason I'm wondering this is I have the sales/ordering guide for the 2100A and the 2100S, and both only specify the 8-bit duplex register. Most Strange! My earlier comments were based on the HP sales/ordering guide, and in retrospect you're quite right, those guides were almost certainly revised from time to time and earlier ones than mine might indeed use the old style reader board. Again, I'm wondering if it's not the A reader that used it? interface site wrong or drawing incorrect conclusions): The 2100 machine is a 2100 machine. 2100 was not a family or class of machines, it was a specific machine (2100 with option pack A or S). There is no difference in the A and S versions except the S version included options as standard which were also available not referred to as "2100's", they were referred to as 2114/5/6. Part of my basis for this is logical - they wouldn't name the 2100 (which came later) a 2100 if that was the generic family name for the 2114/5/6 machines I'm guessing. The early nomenclature of HP's mini products is *SO* confusing... cpu's that were called 21MX's were later redesignated 1000 machines, etc. Plus the whole 2000 thing that doesn't refer to a computer, but rather a specific configuration of both hardware and software (for TSB). What a mess. What's your take on this Bob? Regards, Jay West