In a fixed-mobile convergence (FMC) network environment, convergence between legacy PSTN and ISDN and mobile networks is a typical example of a pre-IMS FMC network environment. ITU-T Recommendation Q.1763/Y.2803 defines the service features, service architecture, and capability requirements of the convergence service between legacy PSTN and ISDN and mobile networks. An example of the implementation of the converged service is provided.