Does anyone know of a decent guide to creating Dial Plans on a Vigor IPPBX?

The manual is utterly useless as it simply paraphrases (very badly) what's displayed on the page on screen. In some cases the explanation is totally unintelligible. Has anyone written a decent guide to this aspect of setting up a Draytek IPPBX?

Also, is it only me that would like to see Dial Plans applicable to only specified extensions? IOW, each extension could be linked to a digit map and there can be multiple digit maps. Most specialised digit maps would only be applicable to some extensions and not others so if it's all just global, the functionality is severely limited. Other IPPBXs I've looked at have no such limitation.

Seems no-one on this forum is using dial plans, but I'll continue the dialog with myself in case anyone feels the urge to chime in.

I have a rule in the digit map that looks for a certain 5 digits (area code) at the beginning of the dialled number and in which case, send it via the PSTN trunk without modification. The backup trunk is the default trunk for that extension.

The idea is that for extensions that include PSTN as an available trunk, that will be used. But if PSTN is NOT available for the extension, it will simply use the default trunk for that extension. This means that the rule only actually applies to those extensions specified as able to use the PSTN trunk - there's no other way to specify that a digit map rule applies only to certain specified extensions and in theory, the above should work since the manual states:-

"Backup route will trigger when defalut route not registed or receive fail response"

So, according to that, since the NON availability (to that extension) of the PSTN trunk creates a 'fail' response (as can be seen in the call detail record) the default trunk for that extension should be used. BUT IT IS NOT. The IPPBX attempts to use the PSTN (which it cannot) and then gives up with a 404 at the client device. So no attempt has been made to use the default route for that trunk.

Anyone else seeing this?