This is an edited version of a post that originally appeared on a blog called The Michigan Telephone Blog, which was written by a friend before he decided to stop blogging. It is reposted with his permission. Comments dated before the year 2013 were originally posted to his blog.
… And Ward Mundy of Nerd Vittles and PBX in a Flash has one for you. The explanation and instructions are here, and the file is here.
(And for all you people who say my articles are too verbose, take THAT!) 🙂