[Simh] pdp11 - console input with high bit set

[David Gesswein]

On Fri, Jul 24, 2020 at 06:12:17PM +0000, Paul Moore wrote:
> Not helped by not knowing what KSR really means.
> 

Keyboard send receive. A model 33 teletype without paper tape.
ASR was the model with paper tape, Automatic send receive.

DEC used teletype's that generated mark parity. From the manuals keyboards were
available to generate other parity. A reasonable amount of old code for
PDP-8's assumed mark parity. Later code ignores the upper bit.

I thought the high bit setting would be turned off if you used set tti 7b or
8b but never verified.