This European Telecommunication Standard (ETS) defines the requirements for the handling of network addresses for the identification of entities which use telecommunication services offered by Private Telecommunication Networks (PTNs). The standard covers numbering@ including the requirements for the support of a Private Numbering Plan@ and the support of subaddressing. The use of more than one PTN numbering plan in a single PTN is excluded from the scope of this ETS. However@ this ETS does not exclude the possibility that physical equipment may be part of more than one PTN. NOTE 1: The application of this standard to entities without fixed geographical locations is not precluded@ but is not explicitly provided for in this standard. This ETS is applicable to Private Telecommunication Network Exchanges (PTNXs) and to terminals to be attached to the access of PTNXs.