A question: 5 different devices use RS 232 as a communication protocol
    to/from a controller (or PC). I need to combine those lines to ONE RS
    232 line.

    tried to find a commerciallay available box that is doing this magic
    trick - and almost suceeded. I don't have time to design the thing, and
    wonder if anyone out there know where I can buy one :=)

What you want is called a "multiplexor."  Usually for async traffic you
want a "statistical multiplexor", which allocated trunk bandwidth to the
ports generating data at the tim, rather than a TDM box that gives every
port a slot whether it has data or not.  Lots of vendors.  (www.statmux.com
was one that popped up quickly.)  Not particularly cheap. "5" is likely to
be an inconvenient number...

A special case of statmuxes is a "terminal server" running a networking
protocol over a wan link of some kind.  The cheapest implementation is
likely to be a couple of obsolete PCs with multiport async cards (6 ports
worth) and linux running SLIP or PPP on one of the ports, and
telnet/telnetd things on the other ports.  Or perhaps some
couple-generations-old commercial equipment - I saw someone selling
cisco-500 terminal servers for $250 each.  One of those has 16 ports and
should do a servicable job...

BillW

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