Updated 05-XI-2011
Cap Nomenclature
Bulb Nomenclature
Filament Nomenclature
Operating Principle
Gas Filling Effects
Filament Coiling Effects
Vacuum vs Gas-Filled
Gas Filling Types
Burning Position
Voltage Variation Effects
Starting Characteristics
Lamp Life
End of Life & Fusing
Premature Failure
Lamp Designs
Carbon Filament
Tantalum Filament
Osmium Filament
Tungsten Filament
Advanced Filament
Infra-Red Recycling

Filament Nomenclature

There are a number of different 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 industrial standard.

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 the shape of the mounted filament, according to the illustrations shown in Figure I4.

Figure I4 - Filament Mount Shapes