ISO 2047
ISO 2047 is a standard for graphical representation of the control characters for debugging purposes, such as may be found in the character generator of a computer terminal; it also establishes a two-letter abbreviation of each control character. The graphics and two-letter codes are essentially unchanged from the 1968 European standard ECMA-17 and the 1973 American standard ANSI X3.32-1973. It became an ISO standard in 1975. It is also standardized as GB/T 3911-1983 in China, as KS X 1010 in Korea, and was enacted in Japan as "graphical representation of information exchange capabilities for character" JIS X 0209:1976 .
While the ISO/IEC 646 three-letter abbreviations, or caret notation are still in use, the graphical symbols of ISO 2047 are considered outdated and rare.