Incandescent light bulb granted a Hungarian patent (No. 34541) for a tungsten filament lamp that lasted longer and gave brighter light than the carbon filament. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1904. This type is often called Tungsram-bulbs in many European countries. Filling a bulb with an inert gas such as argon or nitrogen slows down the evaporation of the tungsten filament compared to operating it in a vacuum. This allows for greater temperatures and therefore greater efficacy with less reduction in filament life. In 1906, William D. Coolidge developed a method of making "ductile tungsten" from
Phase-out of incandescent light bulbs instantly at any temperature, their extremely long lifetime is unaffected by cycling on and off, they have no glass to break, and they don't emit UV rays that fade colored materials. LED lamps radiate almost no heat, and can be either multi-directional or unidirectional, eliminating the need for a mirrored reflector in the bulb or fixture. LED lamps can emit saturated colored light. Disadvantages include spectrum limitations due to discrete emission colors, and higher up-front cost than incandescent bulbs. Botswana has an exchange program distributing CFL bulbs. Of the members of ECOWAS, Cape Verde, Guinea, Mali, Nigeria, Benin and Togo