There are a number of different tungsten filament mounting styles that have become standard over the years. These are not specified in any national or international standards, but a comprehensive system of nomenclature was introduced by general electric around 1910. It has been adopted by a majority of other lamp manufacturers and thus exists as a kind of unofficial definition. The system consists of a two-part coding. The first letter identifies the type of filament wire employed (S = Straight Wire, C = Single Coil, CC = Coiled Coil, FC = Flat Coil, R = Ribbon, B = Braided). The second part is a number which indicates tungsten filament shape, according to the illustrations shown in the following figure.