The best reference is this forum. Search for "digit map" or "dial plan" user RonR. This is a good start:
http://www.obitalk.com/forum/index.php?topic=34.msg17057#msg17057Here's a very rough guide:
The Phone Port DigitMap states what numbers / number formats are allowed to be dialled from the Phone Port. If a number is allowed, then the Phone Port OutboundCallRoute decides where that number is sent. For the purpose of this discussion imagine that there is only one giant Phone Port DigitMap and one giant Phone Port OutboundCallRoute. By referring to other digit maps such as Msp1, Msp2 etc, those digit maps become part of the overall Phone Port DigitMap and Phone Port OutboundCallRoute.
In your particular case, I have added 933 to the Phone Port DigitMap, so now 911 and 933 are allowed. When you dial 911 or 933 the Digit Map Processor will pass the digits through the Phone Port DigitMap and decide they are allowed. The number will then be passed to the Phone Port OutboundCall Route. There the whole number will be compared to each rule from left to right in turn and the first rule that matches will be implemented. In this case rule {(911|933):sp2} will match either 911 or 933 and send it directly to sp2.
I hope that helps - it certainly helps me to think about it every so often
