[COFF] 52-pin D-Sub?

[Clem Cole]

below...

On Fri, Feb 28, 2020 at 5:26 PM William Pechter <pechter at gmail.com> wrote:

> Could it be because they all started with current loop tty interfaces?
> Most of the old DEC guys started with teletypes.
>
Very possible...





>
> Having struggled with a breakout box and different mini and micro vendors
> implementations of serial ports... Ugh.  And in three-wire the use of
> Xon-Xoff varied big time.   No standard was the standard.  IIRC the IBM
> Series/1 had a different 9pin layout than the PC/AR.  Why?
>
RS-232A/B/C was DB-25 P for the DTE (terminating equiment - a.k.a.
terminal) and S for DCE (communications equipment - a.k.a. modem).  It was
standardized.  At one time, I (sadly) could quote the paragraph number....


Then in 1978 #$%^& Lear Seglier put a DB-25S on a DTE (terminal).   They
were the cheap terminal vendor and all hell broke loose.

The PC/AT used 9 pin because the back of the unit was small and -- well
there could because IBM said so ....  But at least the IBM engineers kept
to Plug and Sockets from the standard.  I did not know the Series/1 used 9
pin.   Learn something new.




>   At least DEC was reasonably consistent until they moved too the Vax
> modified RJ design.
>
Indeed - that was a huge issue - the modified RJ block -- sigh...



>
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