This Standard is intended to serve as a guide in the coordination of system design to promote uniformity of the nomenclature and description of the operator devices. Because of the many varied machine applications@ it is recognized that variations and special functions will be required; no attempt has been made to cover all these special functions in this Standard. The definitions used in this Standard are considered to be the minimum function requirement for the device described. If any of the functions described in this Standard are used in a numerical control@ they shall provide the function as defined in the Standard.