Nachwahl

16:09 Oct 21, 2015 

Direct inward dialling number (extension)

It is something like the DID service (direct inward dialling) that enables the direct acces to any recipient within a communication system.

http://whatis.techtarget.com/definition/Direct-Inward-Dialin...
"Direct Inward Dialing (DID) is a service of a local phone company (or local exchange carrier) that provides a block of telephone numbers for calling into a company's private branch exchange (PBX) system.
Using DID, a company can offer its customers individual phone numbers for each person or workstation within the company without requiring a physical line into the PBX for each possible connection. ....."

http://www.voip-info.org/wiki/view/DID
"... In a business with DID, the phone company uses DID signalling to identify the number they are about to connect to the business's PBX. Historically, this was done by pulsing the last 3 or 4 digits of the number being dialed before connecting the number. The PBX would use these DID digits to switch the call to the right recipient"