Date   : Tue, 30 Jul 2002 20:35:02 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: BBC to Mac Link Lead

In article <1026984820.2397.11.camel@...>, Philip Blundell
<pb@...> writes

>They never existed.  The socket is exactly symmetrical, with the two
>"notches" 180 degrees apart.  It wouldn't help at all if the plug had
>two notches: you would still be able to put it in both ways round.  

I had been led to believe that this was a deliberate move on Acorn's
part. 

The RS232/423 interface defines "DTE" (data terminal equipment) and
"DCE" (data communication equipment IIRC) devices.  These have the
transmit/receive and request to send/clear to send pins reversed.  

Thus it was envisaged that it would be possible to make a Beeb a DCE or
a DTE just by reversing the domino plug, providing for a "standard"
cable which would provide two functions.  Those of you reading this who
had to make up RS232 cables to connect a variety of equipment can stop
laughing now [1] :)

No idea whether this is true or not, but I offer it for what it's worth
as an interesting data point.


[1]  in reality, this was a joke, as the RS232 "standard" was so wide-
ranging and ambiguous as to be interpreted in wildly different ways by
different equipment manufacturers.  However, with the use of a breakout
box, it was usually possible to get two different devices talking to
each other.

-- 
     Security-wise, NT is a server with a 'Kick me' 
     sign taped to it.         -- Peter Gutmann