This document defines technical requirements for number portability as they apply to operator services switching systems. It describes the network capability for handling operator services involving portable numbers. The network capability functions in conjunction with the capability described in ATIS-1000002@ and ATIS-1000003. The operator services call types (i.e.@ methods for reaching an operator) to which this document applies include Toll and Assistance (0-@ 0+@ 1+ screened@ 00-@ 1+ 800/888/etc.@ and international prefix equivalents)@ Listing Services (Directory Assistance - 411@ (NPA) 555-1212)@ and Intercept Service (changed number@ discontinued service). This network capability@ Operator Services with Portable Numbers (OSPN) as defined by the requirements in this document@ is available for calls received with either Signaling System No. 7 (SS7) or Multi Frequency (MF) signaling. However@ certain aspects of OSPN require SS7. This network capability applies to service provider portability with location portability within a rate center@ including portability between wireline service providers and the impacts on the functions performed in the wireline network. This document only addresses facility based service providers. This network capability encompasses operator services provided in the wireline network as part of the wireline network's operator service. Requirements in this document apply to operator services switching systems. Network capabilities pertaining to database architecture@ internal switch call processing@ and network operations and administration are beyond the scope of OSPN. The terms Number Portability (NP) and Local Number Portability (LNP) are used interchangeably within this document. Purpose OSPN supports both routing and billing functions for portable numbers. The operator system may need to determine the network location of a called party number for routing and the network location of one or more of the calling party@ called party@ and billing numbers for billing. When it is available@ service provider information may reduce the need for network location information for billing purposes.