Doug writes:

> It could be that the printer is waiting for a DTR from the system. Many
>  printers will happily ignore good data coming down the line if DTR is not
>  high.
>
>  Try jumping pins 4,6, and 20 on the printer side and see if it starts
>  working.

Doug is absolutely correct about DTR; a lot of printers do use this method of
flow control. If you have the manuals for the printer, you can either do what
Doug suggests -- or perhaps better yet would be to switch the method of flow
control that the printer is using. DTR might be listed under the phrase:
"hardware handshake", when in fact what you want is XON/XOFF to provide
maximum compatibility with the DTC.

And to add complications to your life, some printers like the old Texas
Instrument 800 series often required both the DTR line to be held high and
XON/XOFF flow control enabled to work. (Actually, that isn't wholly correct;
you could take the printers apart and reseat their jumpers to get a more
HP3000-like printer, but that isn't the way that they were configured by
default.)

Wirt Atmar