PSTN Access Prefix

The PSTN prefix is defined on a country basis. It is specified for each service provider for each country and each customer in the country. When the caller dials a PSTN number with a PSTN access prefix (typically a 9 in the United Kingdom and United States), this tells the dial plan that the caller is making an off-net call.

When the caller dials the PSTN breakout number, the dial plan routes the call to the correct PSTN breakout location, whether it is a central or a local gateway.