INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : Q.81.2

Title :	Stage 2 description for number identification supplementary 
	services

Study Group : XI - Switching and Signalling

Version : New

Date of adoption : 1992

Notes :	


Recommendation Q.81.2 defines the stage 2 of the Multiple Subscriber 
Number (MSN) supplementary service for the integrated services digital 
network (ISDN) as provided by telecommunications operators. Stage 2 
identifies the functional capabilities and the information flows 
needed to support the stage 1 service description. The stage 2 
description also identifies user operations not directly associated 
with a call (see Recommendation I.130).

This Recommendation is specified according to the methodology 
specified in Recommendation Q.65.

Recommendation Q.81.2 does not formally describe the relationship 
between this supplementary service and the basic call, but where 
possible this information is included for guidance.

In addition, Recommendation Q.81.2 does not specify the requirements 
where the service is provided to the user via a private ISDN. 
Recommendation Q.81.2 does not specify the requirements for the 
allocation of defined functional entities within a private ISDN, it 
does, however, define which functional entities may be allocated to 
a private ISDN.

Recommendation Q.81.2 does not specify the additional requirements 
where the service is provided to the user via a telecommunications 
network that is not an ISDN.

The MSN supplementary service provides the possibility for assigning 
multiple numbers to a single public or private access.

This allows e.g.:

	1) a calling user to select, via the public network, one or 
	   multiple distinct terminals out of a multiple choice;

	2) to identify the terminal to the network for the application 
	   of other supplementary services.

It is considered:

	-   that in the case of a basic access some service providers 
may not have knowledge or control over what is connected, e.g. a 
private ISDN or a terminal configuration;

	-   that service providers have differing numbering methods.

The MSN supplementary service is applicable to all telecommunication 
services.

Recommendation Q.81.2 is applicable to the stage 3 Recommendations 
for the ISDN MSN supplementary service as defined in 
Recommendation I.130.



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