Okay, I have a DEC 3000 300X.  It appears to work.  But of course it's
designed to work with DEC keybaords and mice.  There's nothing wrong
with this, except that I don't much like DEC keyboards and mice.

I'd like to connect up other devices - possibly a different keyboard,
possibly another machine's serial port doing appropriate reprocessing.
But for this I need to know the electrical interface specs.  What
indications I have found indicate that the basic protocol is simple
4800-baud async serial, and I've found source code that describes the
protocol layered on top of that.  What I haven't found is anything that
describes what's _below_ that: the connector pinout(s), whether the
interface is voltage-level or current-loop, what the voltages or
currents are, what sort of power (voltage and current capability) is
provided by the host, that sort of thing.

Anyone have this information for the keyboard/mouse port of a
3000-300X?  Or know where I can find it?  I did some searching but
turned up nothing of any use; perhaps I just never found the right
search terms.

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