LK201 emulation

Ethan Dicks ethan.dicks at
Mon May 18 16:43:33 CDT 2020

On Mon, May 18, 2020 at 5:20 PM Electronics Plus via cctalk
<cctalk at> wrote:
> Do you guys want original LK201s, or other keyboards that LOOK like LK201s
> in the caps and layout, or converters?
> I am a little confused...   LK201 clones do not have the clip offset on the
> terminal connector, so you would have to replace the connector. I have no
> idea if the protocol, voltage, etc is the same.

LK201 keyboards and variants (LK401, clones, etc) have a narrow 4p4c
"handset jack" connector, not offset like an MMJ serial connector.

The power is +12V, the serial protocols are the same.  I've used
LK401s on VT220s and Rainbows, I've used LK401s and LK201s on a Planar
terminal with an "LK201" input jack.  That part is standard.

Speaking for myself, I have a pile of devices (DECmates,
Professionals, Rainbows, VT220, VT240...) that have a 4-place narrow
handset jack for a keyboard, and most of them are expecting an LK201.
I also have a large assortment of LK201s (with and without the WPS/EDT
"Gold Key" keycaps) and 1-2 smaller but compatible keyboards.  Every
time I pull an LK201 off the shelf, I'm wondering if it's going to
work.  I have 2-3 dead ones for sure.  I think at least one of them
has a dead matrix because IIRC, it was causing "4 - keyboard error"
until I dismantled it and unplugged the mylar keyboard matrix sheet.
I suspect that the paint layer has either oxidized to high
resistance/open circuit or there's a short somewhere.  I haven't
investigated that further.  I am also aware of some electronics
failures.  I can obviously mix and match bits to have as many working
keyboards as possible, but that is a finite decreasing number.

What I would find handy in one regard is being able to use a PS/2 or
USB modern keyboard on 1980s DEC equipment as if I was plugging in an

I would also probably employ a device that I could plug a real DEC
keyboard into but that talked PS/2 or USB to be able to use that with
a modern machine.  One application would be to use it with Simh or
even just a dumb terminal emulator (Glass, etc) with a real terminal

I might employ a device that replaced the electronics in a dead LK201
but I wouldn't need that many of them.


> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Sophie
> Haskins via cctalk
> Sent: Monday, May 18, 2020 3:41 PM
> To: Paul Koning; General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: LK201 emulation
> I would absolutely be interested in this - while I'd love to use original
> hardware where possible, it's not always easy to get peripherals at the same
> time as machines. A long term dream of mine is to build some sort of
> general-purpose box that can make connections to arbitrary vintage computer
> keyboard/mouse/video ports, and connect in to modern HDMI & USB peripherals
> to make it easier to just pull a machine off the shelf and get going.
> > On May 17, 2020, at 5:13 PM, Paul Koning via cctalk
> <cctalk at> wrote:
> >
> > Gentlepeople,
> >
> > I've been having problems with broken LK201s, so as a workaround I created
> an adapter that connects to a standard PC USB keyboard and makes it look
> like an LK201.  It's based on an Arduino (specifically, Adafruit Trinket M0,
> an amazingly tiny yet powerful small microprocessor).
> >
> > It's working at this point, though it needs a few small software tweaks to
> make it complete.  I'm going to turn my breadboard into something slightly
> more polished.
> >
> > Question to the list: is this something that would be of interest to
> others?  If yes, I can make the design available.  Perhaps the PCB layout
> and parts list.  I don't think I want to get into building units for others,
> though.
> >
> >       paul
> >
> --
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