An online database of what switches control what NPAs. Useful if you want to see what company any given number block is assigned to. For instance, if you have a number xxx-yyy-zzzz, you can lookup the xxx-yyy portion and see who its assigned to. Due to number portability, this isn't an authoritative way to tell who is currently using a given number, but it might yield a clue about where it started.

BellMind.net Phreakery Tools