The standard applies to controller-device interfaces that provide defined interfaces between low-voltage switchgear, control gear, control circuit devices, switching elements and controlling devices (e.g. programmable controllers, personal computers, ect.). It may also be applied for the interfacing of other devices and elements to a controller device interface. The standard specifies requirements for controllers and devices utilising these interfaces, including not only the communication protocol specification, but also associated relevant electrical and mechanical characteristics. It also specifies the electrical and EMC tests required to verify the performance of each controller-device interface when connected to the appropriate controllers and devices. Part 1 establishes a consistent terminology and format for the subsequent interfaces. It also harmonises requirements of a general nature in order to reduce the need for testing to different standards, increase understanding and facilitate comparisons of controller-device interface standards. Those requirements of the various controller-device interface standards which can be considered as general have therefore been gathered in part 1.