This International Standard specifies an interface system between a single or multiple controlling device and control circuit devices or switching elements as defined in IEC 60947-5-2, connected by a shielded, twisted four-wire cable carrying data and power, and establishes a system for the interchangeability of components with such interfaces.The object of this standard is to define, for smart distributed systems (SDS) interfaces:- requirements for interfaces between control devices and switching elements;- normal service conditions for devices;- constructional and performance requirements;- tests to verify conformance to requirements.