This Recommendation 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 [1]). This Recommendation is specified according to the methodology specified in Recommendation Q.65 [2]. This Recommendation 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@ this Recommendation does not specify the requirements where the service is provided to the user via a private ISDN. This Recommendation 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. This Recommendation 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. Note ?C 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: ?C 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; ?C that service providers have differing numbering methods. The MSN supplementary service is applicable to all telecommunication services. This Recommendation is applicable to the stage 3 Recommendations for the ISDN MSN supplementary service as defined in Recommendation I.130 [1].