Bellcore built on earlier work done by Bell Labs on the intelligent network (IN) and defined AIN in the early 1980s (see Figure A-3). The initial AIN release was intended to provide a generic and modular set of tools to enable the creation, deployment, and management of services on a flexible basis within the public switched telephone network (PSTN). The software tools yielded a suite of service offerings accessible to all network switches, but operating independently from the switch logic. The services, therefore, can be defined, developed, and deployed quickly, and in a multivendor environment. Subsequent releases defined switching and database functions and the interactions between them. AINs include service creation toolkits, which enable the creation of centralized logic residing in centralized databases for the development and delivery of features across the network.AINs support all ISDN features and are intended to provide support for personal communications services (PCS), which permit subscribed features to be supported across networks of all types. The AIN architecture, as illustrated in Figure A-3, requires Common Channel Signaling System 7 (SS7). In addition to SS7, AIN comprises the following components.