To create a new location, go to that Dialing Properties screen and hit
   "New location". Many TAPI apps provide a Dialing Properties button
   which opens your location's properties. Each new location can have its
   own area code, country code, dial-out access rules, even calling
   cards. Be sure to set each of these when you create a new location.
   This is pretty cool because you can keep the number entries themselves
   the same, and TAPI knows to use different dialing rules depending on
   your location.
   
   Apps will let you pick your dialing location just before you dial your
   number. When you swap locations the digit string will change to
   reflect your current location. The one exception is MS Fax, which asks
   you for your location when you run the New Fax Wizard.