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Practical VoIP Using VOCAL by Luan Dang, Cullen Jennings, David Kelly

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Dial Patterns

Dial patterns enable the UA to send completed phone numbers or URLs to VOCAL. These patterns include a set of variables that match commonly dialed numbers, such as 411 or 9-###-####. Dial patterns can also match dialed IP numbers or URIs. Unlike dial plans, dial patterns do not provide routing information, they simply let the UA know that a completed number has been dialed and can be sent to VOCAL for routing.

There are two timers at work with dial patterns. First, the Initial Digit Timeout clocks the time that transpires between the UA going off-hook and the first digit being entered. If this times out, the UA will need to go back on-hook, then off-hook again before the user can resume dialing. If the user enters a digit before this timer expires, the Initial Digit Timeout stops, and the Inter Digit Timeout begins.

The Inter Digit Timeout measures the time taken between digit entry and the time the dialed number matches a dial pattern. If the dialed numbers match a specific dial pattern, such as 411, this timer stops and the number is sent to VOCAL. If the user stops dialing but the number dialed does not specifically match any dial patterns, this timer times out and the UA sends the dialed number to VOCAL as is. This method of combining timers with dial patterns helps manage calling and permits variable-length dial patterns to be sent to VOCAL, which is useful for international dialing or local dialing in countries that permit variable-length phone numbers at the local ...

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