International lamp coding system
The international lamp coding system (ILCOS) is defined by IEC 61231, an international standard maintained by the lamp technical committee of the International Electrotechnical Commission. It is intended to provide a well-defined and vendor-independent coding system for all lamp categories except vehicle lamps. The first version of the standard was published in 1993, the most recent update in 2013. ILCOS defines a short code, ILCOS L, and a standard code, ILCOS D, which provides the complete designation of a lamp.