Touch Tone Checker is an Address Book Plugin that provides an additional command to the menu that appears when you click the label next to a phone number. The command will play dial tones for the number in question through the computer’s speaker. Letting you just hold the phone next to the computer’s speaker instead of having to dial the number.
To install Touch Tone Checker, it needs to be placed in a folder named ‘Address Book Plug-Ins’ inside a ‘Library’ folder. You may need to create that folder (taking care to get the spelling right). Holding the Option-key while clicking a phone number’s label will give you a command to adjust Touch Tone Checker’s preferences. In particular you can set up your area code there, making Touch Tone Checker attempt to figure out how to adjust numbers in your Address Book by adding or removing area or international codes to or fom the number.