In asterCRM, we can set some description for a trunk or a DID, so that when customer dial in, we could know which number he dialed or which trunk he dialed from. 
it’s very simple to set this, login as admin and go to management interface, select Trunkinfo, and then add the trunk or didnumber or both. 
this feature could be very useful for a virtual office, say you have some agent in the office, they answer phones for kinds of company, need to say different hello words for different company
