One of the system's internal telephone numbers (subscriber numbers) must be entered in the telephone so that the system recognises the telephone as an internal subscriber. This number must be the one that the telephone is to transmit to the system. This is usually the first MSN entered in the telephone. The same applies to ISDN cards. The internal station number entered in the telephone must of course also be configured in the system as the internal station number of the corresponding internal S0 bus.
If an internal number is entered in the telephone, and this number is also configured in the system, but telephoning is still not possible, then it is very likely that the telephone is not connected to the correct S0 bus. In the system, the internal call numbers are assigned to the individual ports of the system. Therefore the telephone must be connected to the corresponding S0 bus.
The forced assignment of the internal telephone number of the system to an internal S0 port can be switched off by activating the move function.