XYGAX writes:
>If I remember corectly I did some work with a device that only used the busy
>line (a cash till) the printer was conected through this device and the busy
>was flaged when the till opned this stops the flow of char's so if the busy is
>aranged to pulse after each char then this should hold the PC until it is
>released when it can send the next char.

        I want to express thanks for this answer and another response I got
privately.  It sounds like the P.C. parallel port works a lot like the
Apple II port I remember except for the addition of the Busy flag.  I was
wanting to be sure there wasn't a cabling shortcut that I could use to make
the port work without the ACK pin, but it sounds like I will need to build
a delay like was described in the response.  The old device is a Votrax
Personal Speech System, a speech synthesizer that was popular in the early
eighties.  The device has a DB25 mail connector on its parallel port, but
the pinout is totally unlike anything else.  Fortunately, there is a 5-volt
VCC line available so I can power some logic chips.  It just means my cable
will now have an extra box hanging off of it.  Oh well, that's better than
not being able to make it work at all.

        This makes me wonder why have both an ACK and a Busy?  If there is
an ACK pin and the peripheral stops acknowledging characters, then the data
stop, anyway.  At least this tells me that if I ever build something using
a PIC that gets input from the P.C. printer port, I had better leave a
PIC pin to send the ACK each time a new byte is received.

Martin