telephone number block

With ISDN systems, the subscriber can choose between the system connection and the multi-device connection.

The system connection operates with a single telephone number for the PBX and with additional extension numbers for the individual extensions. The extension numbers for the extensions are communicated to the user as two- digit number blocks, the call number blocks. For larger private branch exchanges, three-digit number blocks can also be requested from the RegTP.

A two-digit number block can include numbers between 00 and 99.