This section of IEC 870-6 specifies the protocol for the services provided by an application service-element – the Telecontrol Application Service Element no. 1 (TASE.1) – to support the exchange of process data between telecontrol systems. The main goals for the design of these services are: – simplicity; – adaptability; – independence of lower layer architecture; – extensibility; – efficiency; – performance; – maintainability. The services of TASE.1 are: – services for defining, changing, deleting and inspecting groups of information; – services for managing the transfer of information groups and blocks of information from different groups; – services for supervisory control. This section of IEC 870-6 specifies the protocol (abstract syntax) and the procedures for the Telecontrol Application Service Element (TASE). The TASE.1 services are provided in conjunction with the Remote Operations Service Element (ROSE) services (ISO/IEC 9072-1) and the ROSE protocol (ISO/IEC 9072-2), and the Association Control Element (ACSE) services (ISO 8649) and the ACSE protocol (ISO 8650). The TASE.1 procedures are defined in terms of: a) the interactions between peer TASE.1 protocol machines through the use of ROSE services; b) the interactions between the TASE.1 protocol machine and its service-user. The scope of the protocol is limited to the interconnection of systems. It does not specify or restrict the possible implementation of interfaces within a telecontrol system.