The external line code pattern used to match dialing strings. This must be in the form of a number or dialing pattern. It cannot contain wildcards. Ending the pattern with '&' will cause the unit to also look for a valid dial-plan pattern following the External line code, however ending it with '$' will cause the unit to stop attempting to match further input. The following rules must be observed: 1. Templates MUST have at least one NUMBER. 2. Wildcards are not allowed. 3. & or $ is allowed but MUST be the last character. Cannot be standalone. 4. If * and # are entered, they must be the first character. May not be standalone.