&H378 255 254 253 252 
The values are  &H378 for the port (LPT1),  followed by the function codes 255 
for no tone,  and 254 for 300 Hz,  253 for 730 Hz,  and 252 for 1800 Hz tones,
respectively.   To select LPT2 change the port address to &H278.  The port and 
function codes could be  chosen  arbitrarily for other tone generator designs.


