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    EEVblog #1054 – How an Analog PC Joystick Works

    How does a PC read an old school analog joystick? It might be more interesting ...

    • Adrian

      I’m not familiar with that particular unit, but looks like a pretty standard KTS (Key Telephone System) from the era. I would have guessed an AT&T product initially, doesn’t look like the Samsung Prostar series. We had a lot that looked like that out here, but painted blue with various names on the side.

      It seems to be in a 6×16 layout (6 trunk lines, 16 stations) without any expansion options, which would be a bit unusual in the US market (would have usually been 4×8 or 8×16 with additional 4 and 8 port add-ons). Each of the RJ11 jacks takes in 2 2-wire trunk lines from the CO. Then 16 4-wire station ports output, each of which contain an audio pair and a signaling pair. Lots of 600-ohm isolation transformers was the norm. Programing requires matching KTS phone station on line 1 (usually a particular model from the series as well) and was an absolute pain in the butt…

      • Bill Clay

        Those RJ21 connections next to the “phone jacks”
        are 50 pin, two pings are not used. So that makes 24 (“4×8”, like Dave said) lines.

        • Adrian

          Those “phone jacks” are RJ11s, 6-position 4-conductor, and each is being used for 2 incoming trunk lines. That makes 6 lines.

          And Dave said 4×8 (32 total, not 24), because he counted up the transformers on the station side of the board. What Dave didn’t know at the time was that these KTS/KTU systems often used 4-wire stations, as both I and Tony stated… Each station has an audio and a signaling isolation transformer. That makes 16 stations.

          You can;t really tell anything by the number of pins in the RJ21 (more often referred to as an Amphenol connector, or just “25-pair”). It could have all the stations in one connector, or like this one spread across several connectors. Some of the extra pairs will the used for the MOH input, page port, relay output, inhibit input(s), PBX bridges, etc… Some will have no connection at all. You would have to have the manual to tell the exact pinout used.

    • That 616 indicates 6 central office lines and 16 extensions capacity on the system.

      And yes, these were hybrid systems with voice on one pair, data on the other.

      For my money the best KTS type systems were the old 1A2. Not a lot of functionality beyond hold features, but they were built to withstand serious abuse. It’s just that the 25 pair wiring was a bit of a pain.

      Next fave after that is the Partner systems. They had all the features present in the 1A2 and added some.

    • Felix

      Dave, I can’t believe you chose Victorinox over Leatherman. Leatherman is the Fluke of multitools! Tsk tsk…

    • Uncle Vernon

      It was left for you for a reason.

      You’d pay as much for two second-hand (euwww) handsets as you would to buy a modern replacement.

    • Nick

      Forget about this monster of telephony system and build yourself an Askozia PBX. Using that with the cheapest SIP phones in the market, you can connect over Internet your home phones and your Android mobile phone(s) too.
      No more telephone bills for you to pay, plus increased functionality.

    • salec

      Z84C00 is venerable Z80 CPU in CMOS, but you probably new that already (unless you were one of Commodore 64 fans back then, not Sinclair’s). You can probably find a free disassembler download somewhere online, read the PROM and find out what it does … if you have time on your hands.

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