BusinessPhone Communication Platform 5.1
Facilities

## ISDN SS Multiple Subscriber Number (MSN)

## Definition

The supplementary service MSN provides the possibility to assign multiple ISDN numbers for a single interface.

In ASB 150 02 this function is used for the S -Interface in order to reach each ISDN terminal on the bus by dialling its programmed MSN number.

## Use

This feature allows a direct addressing of the ISDN terminals or the ISDN interface.

## Operation

Each S-Interface and each connected ISDN-terminal supporting its own MSN requires a directory number in ASB 150 02.

These ISDN directory numbers will correspond to route access numbers (see also ISDN S‑Interface).

### Incoming call to the S-interface

#### MSN is supported by the ISDN terminals on the S‑interface

Each ISDN terminal can be reached directly by dialling its assigned MSN.

When the ISDN terminal answers the call, its programmed MSN will be sent back as connected number.

#### MSN is not supported by the terminals on the S‑interface or the use of MSN numbers isn’t permitted by programming

Only a global call can be initiated to the S-interface. Each ISDN terminal compatible to the offered bearer service can answer the call.

If MSNs are not permitted on the S-interface, and route numbers as well as the terminals are programmed with MSNs, the called party number will be discarded in the call setup message and a global call will be initiated.

### Outgoing call from the S‑interface

#### MSN is supported by the ISDN terminals on the S‑interface

If the MSN is provided by the terminal, this number will be used in the call setup message as the “calling number”.

If an ISDN terminal with a programmed MSN but with no assigned directory number in the system initiates a call, the calling party number will be discarded in the call setup message, and the common directory number of the S-interface will be used instead.

#### MSN is not supported by the ISDN terminal or the use of MSNs is not permitted by programming.

If an ISDN terminal initiates a call and there is no MSN available, the common directory number of the S‑Interface will be sent as the calling number.

If a terminal has a programmed MSN, but the programming does not permit it, the calling party number in the call-setup message will be discarded and the common directory number of the S‑interface will be sent instead.

## Capacity/Limitation

As mentioned before the MSN refers to a route access number. A maximum of 255 routes may be configured in the system (including all individual and common numbers).

## Programming

### ASB 150 02

5401 |  | Create route

3201 |  | Route members

1956 |  | MSN provided to TEs?

### ISDN terminal

For programming the MSN see User’s Guide of the ISDN terminal.

## Equipment

BTU-B_ or MFU.

Revision: K © Ericsson Enterprise 2003