Others have reported on the pin names but you need to remember that there
are several more pins on the computer end that may need to be tied together
in order to get the computer to output a signal.
Voltages are typically about +/-9V or so. Anything more than 5V is good for
a signal level although the computer will put out something between 9 and
12V ususally.
At the machine end with only 3 pins, one will indeed be tied to an
electronic ground, one will have a definite voltage on it and the third will
usually just be seemingly open.
If you don't have an original cable (even with a broken wire inside) you can
fight the problem for a long time if you don't know what is happening with
that system.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!