The DrayTek VigorBX 2000 uses Digit Map to route outbound calls based on the number dialled. This checks the number dialled against the Digit Map entries in order, from the first entry to the last entry with the PBX routing the call based on the first match.
When a number is dialled, the PBX checks the length of the number of the Prefix / first digits of the number to check against Digit Map entries with these options available:
If the number length dialled and prefix dialled match a Digit Map entry, it would then perform a Method action based upon the Digit Map entry's configuration:
If there is no match or if there is no digit map configured, the PBX system will route calls based on the Extension's Default Trunk setting. If that isn't configured or is unavailable, the call will not be routed and the Extension will be unable to call out.
It is possible to bypass the Digit Map configuration by dialling a Trunk specifically, for instance dialling "001" to select the first SIP Trunk then dialling the number.
This guide demonstrates how to configure the Digit Map entries to perform possibly useful functions such as adding a local area prefix to short local numbers.
To configure a Digit Map entry, go to [IP PBX] > [Dial Plan] > [Digit Map]:
To force all calls to go through a specified Trunk interface, set the Min and Max Length values so that they would cover any calls made through the system, in this example 1 to 15 digits.
For the Match Prefix, specify that as "?" which is the wildcard character. This means that any number between 1 and 15 digits in length would go through SIP-1-DrayTEL trunk in this example.
The wildcard character with no other prefix is effectively a "catch-all" rule; this should be placed after all other Digit Map entries so that other Digit Map entries are still processed.