sandrock@uxc.cso.uiuc.edu (04/06/88)
We run 22 AWG twisted, shielded cabling through a tunnel under the street
to another building. These cables are all more than 500, but probably less
then 1000 feet long. People that need 9600 baud (for graphics displays, etc.)
spend $100-$200 for line drivers, but most PC's and terminals just run at
4800 baud without problem (and have been for years). You might want to try
less expensive cable first, such as 24 AWG twisted, unshielded, if the cost
is really an obstacle, but we mostly only go a few hundred feet with such.
It may be useful to keep in mind that reducing your baud rate will buy you
more distance and saving money on cable MAY tend to cost you distance as far
as reliable connections go. Expensive flat ribbon cable is NOT designed for
distance, unless you pay the premium price for the special low-capacitance
variety, and even then I would choose shielded, twisted pair. The way it is
wired here is to make pin 7 (signal ground) and pin 2 (DTE TxD) one pair,
and pin 7 again and pin 3 (DTE RxD) the other pair. If you have shielding,
it should be connected to pin 1 (protective ground) at one end of the cable
only to avoid "ground loops" (so I've been informed in the past). You will
probably have to include a virtual "null modem" as well, by connecting pin
2 at one end to pin 3 at the other end, ("swapping transmit and receive")
so that both devices are not "talking" on the same line, but check the
appropriate owner's manuals to be certain of this.
Hope this helps,
Mark Sandrock