Interfacing PDP 11/05 to VT 50

Ethan Dicks ethan.dicks at
Tue Dec 1 11:43:32 CST 2015

On Tue, Dec 1, 2015 at 11:55 AM, Paul Koning <paulkoning at> wrote:
> I'm not sure I understand the question correctly.  That article clearly points out the 20 mA wires, and presumably that's where your ASR33 is connected.  The VT50 comes (according to the peripherals handbook) with a standard 20 mA interface, optional RS232 interface.  So it sounds like it would be a matter of finding where the 20 mA connector on the VT50 is, and plugging into that.
> Interestingly enough, the VT52 is listed as supporting either kind of interface, but only one; "specify at time of order".

I don't know that I've taken apart a VT50 or if there are internal
differences, but for the VT52, there's a ~2"x5" (from memory) PCB with
interface circuitry for either EIA or 20mA and a permanently-attached
cable with the appropriate connector on the host end.  You take the
bottom of the terminal off, pop the board, pop the other one on and
it's switched.

It would not be difficult to replicate either board, either by hand or
with a fabricated PCB.


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