From: sje@xylos.ma30.bull.com (Steven J. Edwards)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Serial port connection wire?
Date: 10 Apr 92 15:08:40 GMT
Reply-To: sje@xylos.ma30.bull.com
Organization: Bull HN, Worldwide Information Systems, Billerica, Mass., USA

In article <1992Apr10.003443.1@ilp.mit.edu> gold@ilp.mit.edu writes:
> I have a question about connecting serial ports between PC's.  At a 
> place I work at part-time, we have 5 PC's in different rooms on 
> different floor.  We won't be able to afford ANY networking 
> options for about 1 year and I need to transfer one hugh file (3MB) 
> between computers twice a week.
>
> I have FASTLYNX to transfer files between computers very quickly
> via serial lines.  I would like to temporarily run a few wires 
> through small holes already in the walls between the serial ports.  
> Unfortunately, I know very little about networking wire.  I am 
> looking for some about the diameter of typical phone-cord wire that 
> plugs into an adapter that, in turn, plugs into a serial port.  (I'll 
> take care of pin configurations to be FASTLYNX compatible.)
>
> Does anyone know of inexpensive wire that I can use for the purpose 
> described above.  Thanks in advance for any assistance.

	The RS-232 standard used in most PCs requires twenty five
conductor connections for "full" support.  This is why they often use
DB-25 connectors.  However, most of the 25 pin signals are not used in
typical applications, and the nine pin DB-9 connectors suffice.  To
make your own cables, something I've done many times, is fairly easy
and can be done relatively cheaply.  You will need to buy the do it
yourself connector kits and the appropriate cable.  I've used standard
shielded eight conductor cable, about 1 cm diameter, available at a
few dollars per meter.  It contains eight insulated wires along with
an uninsulated internal shield and covering wire.  (This covering wire
is the protective ground [not the signal ground!] and is connected to
the exterior harness assemblies.)  The eight insulated wires cover the
required eight signals needed for a full modem control connection.

	I tend to wire cables "straight through" without crossover and
then use small null modem attachments as required.  I like to have all
of the cables to have the same predictable, one-to-one pin out.  I
also have most cables be bisex (male at one end, female at the other)
for easy chaining and use small gender changers attachments as
required.

	Everything you need gan be purchased from your local well
stocked electronics supply store.

	The cable must be shielded; RS-232 is very prone to noise
pickup, particularly over long (> 25 m) connects in typical EMI
environments.  Avoid using a cheapshot approach like software flow
control over plastic coated four conductor phone line wire.  You
probably don't want to inadvertently set up an RF antenna and so be
broadcasting your high baud rate data to your neighbors.

	You might want to get a book on computer data comminications
if you are interested in knowing exactly what you are doing with
serial interconnects.

 [The above opinions expressed are my own; not necessarily held by others.]
      == Steven J. Edwards           Bull HN Information Systems Inc. ==
      == (508) 294-3484              300 Concord Road         MS 820A ==
      == sje@xylos.ma30.bull.com     Billerica, MA 01821          USA ==
"That Government which Governs the Least, Governs Best." -- Thomas Jefferson