Connecting Arduino to Payphone Keypad

Hi all, for my latest Arduino project, I need to have my Uno use a payphone keypad as input. Yesterday, I took apart the keypad, and it seems that the keypad has 11 keys, obviously, and 7 pins for output. I talked to my dad, who gave this to me (he used to install these babies in Boston), and he said it uses "Dual Tone Multi Function". How can I connect my Arduino to this? I can't really put my own keypad in, because I need the payphone to work normally still.

You need a DTMF decoder.
Some useful Google terms there

Did you have any success getting this working? I've a payphone keypad I'm trying to connect to and it appears that it's not quite the same as the matrix keypad. Any idea what the pins are for on these?