The Call Manager manages and connects the various subscribers and lines described above with one other. The Call Manager's main task is to determine the correct target subscriber for each call and to select a suitable line for this subscriber. To be able to meet this task, the Call Manager mainly uses two table areas:
- The call routing table
- The tables of local subscribers
As the Call Manager usually switches between internal and external telephone networks with different number ranges, the Call Manager often has to change the numbers that are called, and this is known as number translation.
The procedure known from internal extension lines is used, whereby connections to external subscribers start with a preceding "0". The Call Manager processes calls to and from all registered subscribers and lines.