asterisk users - Apr 2018 - Asterisk / PRI and Outbound Overlap Dialing (Mtt Cannon)

According to Asterisk wiki:
https://wiki.asterisk.org/wiki/display/AST/Pattern+Matching#PatternMatching-SpecialCharactersUsedinPatternMatching

The exclamation mark (!) character is similar to the period and matches zero or
more remaining characters. It is used in overlap dialing to dial through
Asterisk. For example, _9876! would match any number that began with 9876
including 9876, and would respond that the number was complete as soon as there
was an unambiguous match.
 
Asterisk treats a period or exclamation mark as the end of a pattern. If you
want a period or exclamation mark in your pattern as a plain character you
should put it into a character set: [.] or [!].

Mc GRATH Ricardo