10.30.2.1. Multiple Subscriber Numbers (MSN) on the S0 Bus 
With the Multiple Subscriber Numbers (MSN) feature a terminal interface
can be assigned several (not necessarily consecutive) subscriber numbers.
It is thus possible to select a specific terminal from several belonging
to the same service and linked to the same S0 bus.
The bus terminology introduced with AMO SBCSU is used in the following:
- Main Subscriber Number
The main subscriber number in a bus configuration is the number assigned to the physical LINE of the bus. The bus is configured with this subscriber number.
- Secondary Subscriber Number
The secondary subscriber numbers in a bus configuration are additional numbers, under which CorNet terminals can be configured.The bus constellation, functional bus (FBUS) as well as an UP0/E connection with functional terminal can be extended such that an existing functional terminal on the main subscriber number or the secondary subscriber number can be reached via several phone numbers. In contrast to the number conversion with AMO TGER, the phone number dialed by the A station is displayed to the B station. Furthermore, additional functional terminals for a service already configured on this port can be connected and reached under a separate phone number. The previously used bus terminology has to be extended in this case by the term secondary MSN number and MSN phone number.
- Secondary MSN Numbers
The effective range of an existing secondary subscriber number is extended to the existing functional non-voice terminal for the main subscriber number or secondary subscriber number. In other words, the NV-FUNCT terminals for the main/secondary subscriber number can now also be reached via the secondary MSN number if it is configured accordingly. Other FUNCT terminals for the same service that are connected to the bus can be reached selectively with the secondary MSN number. Secondary MSN numbers can occur at the UP0/E port. Secondary MSN numbers can occur at the UP0/E port. Since the first "MSN device" on a secondary MSN number occupies a TSI, the number of secondary MSN numbers on the bus is restricted.
IMPORTANT:
In UP0/E- configurations, functional terminals can also be assigned to secondary subscriber numbers. The main subscriber number can then be assigned MSN functionality, and thus becomes a "secondary MSN number". - MSN Numbers
These are further numbers for functional terminals. All the services for which a functional terminal is configured under the main subscriber number can be accessed under an MSN number. Accordingly, MSN numbers are used in MBUS, FBUS, and UP0/E- configurations. There are no restrictions regarding the number of MSN numbers on the bus.