Yes, I tried different baud rates, and even different parity
conigurations. I really think that it's putting out some kind of data
for the program that the computer is supposed to be running, because I
don't see any readable text in it.

In article TPu4qbPdipCY-pn2-skgnXUDurSGv@tori,
says...
On Sat, 13 Sep 2003 23:59:08 UTC, wrote:

BTS-600 client program with a serial cable. The manual that I have
describes using it with a dumb terminal, but when I connect to it with
Hyperterminal, all I get is garbage on the screen.

If you get garbage, it's more likely to be a baud rate misconfiguration
than a terminal emulation issue.

Hyperterminal -- bah!

Sigh.
I keep a W95c box around for this kind of thing, but its version of HT
is 1995, of course. Poking around just now, I can see that it *is*
possible to convince it to not autodetect the port baud rate, and will
condescend to let you manually specify the rate. I suggest you try each
rate option, one at a time, and see if your garbage become more legible.
Likely rates for industrial equipment are 1200, 2400, 4800, and 9600,
with a few pieces still running as low as 300, and a few more running as
high as 38400. Try 9600 first, then move down. 9600 is a pretty fair
standard.

If the terminal emulation is off, keystrokes won't do what you think
they should, and some (legible) chars may blink, be underlined, or
misformatted, but the ASCII will still be more or less readable.