This European Telecommunication Standard (ETS) specifies the stage 1 description of Support of Private Numbering Plan (SPNP), which enables a subscriber to use a Private Numbering Plan (PNP) for communication across one or more networks with mobile and fixed users. The subscriber may belong to one or more (up to 9 maximum) Private Numbering Plans. The subscriber may also, subject to subscription, have access to the Public Numbering Plan. The structure and content of each PNP are defined by a PNP Manager, although these are out of scope of this ETS. The service is described from the service subscriber s and user s points of view; in particular: - the procedures for normal operation with successful outcome; - the action to be taken in exceptional circumstances; - the interaction with other GSM supplementary services. This ETS does not deal with the Man-Machine Interface (MMI) requirements, but makes reference to the appropriate Global System for Mobile communications (GSM) specifications. The charging principles applied to Support of Private Numbering Plan (SPNP) are outside of the scope of this ETS. Any interactions with other services and/or networks not dealt with in Clauses 4.1 and 11 to 13 are outside the scope of this ETS.