System mode

Key System Mode
Each phone is configured with 2 Intercom buttons which cannot be changed. It is also configured with line appearance buttons for specific lines using the Number of Lines settings and individual button programming.
Internal calls are made by selecting one of the two Intercom buttons provided on each phone and then dialing the number of another extension or of the system feature required.
External calls are made by selecting one of the line appearance buttons programmed on the phone and then dialing the external number required.
If the user dials without selecting an Intercom or Line button first, the user's automatic line selection setting is used to determine which button, if available, gets used.
PBX System Mode
Each phone is configured with 3 call appearance buttons (2 only on ETR phones). These can be used to make both internal and external calls. The dialing of an external call can be indicated by the dialing starting with a specific prefix (9 or 0) if required, otherwise any number not matching an internal extension or function is assumed to be external.
The line used for an outgoing external call is determined by configuration settings. ARS Selectors are created which can be groups of lines or specific functions using any available ISDN lines. Different external number prefixes are then mapped to those ARS Selectors. When a user dials an external number, it is matched to a selector and uses the function and one of the lines specified by that selector.
Line appearances can still be used to make and answer calls on a particular line. They can also be used to make a calls.