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Adapting old Apple RJ11 keyboard to USB

Discussion in 'General Electronics Discussion' started by joepshoulak, Aug 4, 2013.

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  1. joepshoulak


    Aug 4, 2013
    Hey all,

    I recently found an old Mac Plus, that eventually I want to get working. In the mean time, I would like to be able to use the keyboard it came with, as it's all old and clacky. Unfortunately, it comes out 4-pin RJ11, and I can't figure out what to do other than to plug it into a phone line and start sending text messages (kidding).

    How would I go about converting from RJ11 to USB? Would I have to use PS/2 as an intermediary? Can it be bought off the shelf? If not, I'd be fine wiring it up, but I do want to preserve the current cable (i.e. buying a female end and using that) so I can use it with the Mac Plus when (if) I ever get it up and running.

    Thanks for the help!
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    You need to find out what type of keyboard that is. Four wires sounds like ADB (Apple Desktop Bus, see but ADB uses Mini-DIN8 connectors, not RJ11, AFAIK.

    Whatever it is, to make an adapter yourself you would have to use some kind of programmable device, probably a microcontroller. Some micros come with USB built-in - Microchip PICs, at least. And the keyboard protocol will have to be emulated. And there will probably be key mapping issues that may need to be thought about carefully.

    I guess it's possible that such a device may be available, or may have been designed as a project. I'll leave the Googling to you - probably ADB USB keyboard would be good keywords. Assuming your keyboard is ADB.

    Good luck!

    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
    Here's a thought. Why not plug it into the Mac's keyboard port. :rolleyes: This video seems to indicate that the Mac Plus has a keyboard port (RJ11) on the front of the computer.


    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
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