[Asterisk-Users] How to allow users to dial certain numbers

[Ronald Wiplinger]

I am not sure how I should call it, .... so I cannot find it in the wiki 
either ;-(

I want that extension 601 can dial every number (extension, function 
like wake up, dial out at each line, long distance call, international 
calls, ....)

602 should only get a limited set of allowness.

A dialin user from a pstn should be allowed to dial out at another 
gateway (pstn) if he has a prepaid card .....

How can I build up such restrictions?

bye

Ronald