Steve Olney wrote:

[....]
Alberto - a question for you.    How many lines can you set/reset reliably
from a serial port ?    This would set the maximum number of tone
frequencies.

73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)

Steve and the group,
  I don't have handy in this moment the API Reference, but I am afraid that
the old trick used with the good, old DOS of using the status lines of the 
serial
port as parallel output lines is not available when working with Windows.
With Bill's baby, the only possible use of the serial port is that of, well, a
"serial port"  :-) , unless I stand corrected after having perused the APIs.

If you need parallel output lines, then the printer port seems to be the only 
choice,
unless you put an UART or a shift register connected to the serial port.
I don't have enough info on the USB port to be able to comment on this latter.

But, if you don't need to transmit more than one frequency at the same time,
the 8 data bits of the parallel port allow for 256 tones, which should suffice.

73  Alberto  I2PHD