Revision Standard - Active. The definition and application of function numbers and acronyms for devices and functions used in electrical substations and generating plants and in installations of power utilization and conversion apparatus are covered. The purpose and use of the numbers and acronyms are discussed, and 95 numbers and 22 acronyms are assigned. Function numbers or function acronyms now exist for arc flash detection, clock or timing source, dynamic disturbance recorder, digital fault recorder, disturbance monitoring equipment, environmental data, fault data concentrator, high impedance fault detector, human machine interface, historian, scheme logic, substation metering, phasor data concentrator, phasor measurement unit, power quality monitor, remedial action scheme, remote input/output device, remote terminal unit/data concentrator, sequence of events recorder, and trip circuit monitor. The use of prefixes and suffixes to provide a more specific definition of a function is defined. Device contact designations are also covered.