Important: If you must prefix e.g. an exchange line access number when entering/selecting a phone number, depends on the exchange line request (automatic, direct exchange line telephone, internal telephone) that was configured in the PBX (see Advanced Information of the PBX). Exception: With the PBXs COMpact 2206 USB and COMpact 4410 USB in any case external numbers are entered with a leading exchange line access number.