The ///'s plug is female. You will feel dumb trying to plug a
female cable connector into a female RS232 port. You will feel dumber
trying to plug a DIN-8 connector into a DB-25 socket. You will feel
even dumber if you try to force fit the long side of a "D" shaped
plug over the short side of a "D" shaped socket. Your spouse will
giggle at you. Your dog will shun you.
If you already have an RS232 cable
that is mis-plugged, you can buy adapters or "gender menders" at
places like Radio Shack. These may be marginally less expensive than
buying a new cable.
If you want to communicate directly
from your Apple /// to another computer in the same room, you need a
special cable called a null modem or a modem eliminator. The RS-232
port on each machine thinks it is talking to a modem. The pins are
set up that way. If you don't have a modem between the two computers,
you need to re-define the pins. A modem eliminator switches a couple
pins so that both computers think they are talking through modems. A
ten buck modem eliminator is bunches cheaper than two modems.
Null modems and gender menders and
adapters look a whole bunch alike. Some printer cables look just like
modem cables, but they -- like null modem adapters -- switch pins
around. Do not confuse them or you will have a true failure to
communicate. If you have a selection of these cables, label each
1.3 Interface Cards
The Apple ///'s built-in serial port
is not the only thing available for data communications. The Apple II
Super Serial Card (or clone) and the Apple Serial Card /// provide
extra serial communications ports. The Apple II SSC is not real good
for data communications because of the card's DIP switches. It is a
real bore to pop your ///'s lid and flip switches on the card when
you want to talk to a different computer. The SC3 does not have that
limitation, but it needs a special driver for data communications
(check the WAP /// SIG PD). Most Apple /// data communications
programs assume you will be talking through the built-in RS-232 port.
You are best off using the built-in port for data communications, and
using slot cards for other "serial" devices like printers.
2.0 Data Communications
Setting up your Apple /// for data
communications involves an Apple /// "driver" file that must be
installed in your boot disk's SOS.DRIVER file. In the general case,
you need never set or change the data comm driver's parameters (the
subject of some truly arcane pages in the Standard Device Drivers
manual). Most data comm programs have commands to set and change the
driver parms themselves. Use the System Utilities Program's "System
Configuration Program" (SCP) to install the driver in your boot disk,
and then forget it.