Certain area code numbers are set aside in the North American Numbering Plan. For example, these numbers are 200, 300, 400, 500, 600, 700, 800, 877, 888, and 900. You must specifically deny calls made to area codes 200 through 900, except 800, 877, and 888.

If you do not want to incur charges, you can also deny access to the 976 prefix. The 976 prefix is set aside in each area code for pay-per-call services. You can block 976 or any other prefix in all Numbering Plan Areas (NPAs) with a single entry in the digit analysis table.

You can set the 200 area code apart from other area codes 201 through 209. We use the digit analysis table 120 because it defines long distance calls that begin with 1 and all area codes from 200 through 209.

In this example, that begins with 120, where the call is permitted. The 120 translation handles all dialed strings from 1201 through 1209.