Bipin

A bipin or bi-pin, (sometimes referred to as two-pin, bipin cap or bipin socket), is a standard from the IEC for lamp fittings. These are used on many small incandescent light bulbs (especially halogen lamps), and for starters on some types of fluorescent lights as well. Some lamps have pins placed closer together, preventing them from being interchanged with bulbs that are too high power, which may cause excessive heat and possibly fire. These are sometimes called "mini-bipin". Some of these, particularly in automotive lighting, have the pins bent back onto the sides of the base of the bulb, this is instead called a wedge base or socket. The bi-pin base was invented by Reginald Fessenden for the 1893 World's Fair in Chicago. After Westinghouse won the contract to wire and illuminate the first electrified fair with AC instead of archrival Thomas Edison's DC, Edison and his General Electric company refused to allow his patented Edison screw-base bulbs to be used. Westinghouse overcame this by inventing the bi-pin base for use at the fair.