To decode, I just loop the touch tone in Cool Edit, then compare it with the buttons I press on a phone. It's quicker than it sounds.
You can also call up a phone company where the automated system asks you to enter your phone number. Then you play the tones into your phone and the automated system responds with, "You entered 8 7 4 3 0 1 9 0 4 8 (or whatever). Is this correct?"