The Edison screw fitting is a system of light bulb connectors, developed by Thomas Edison and licensed starting in 1909 under the Mazda trademark. Most have a right-hand threading, so that it goes in when turned clockwise and comes out when turned counterclockwise, like a hardware screw. There are rare instances where these are reversed to deter theft, so that they cannot be used in other light fixtures.
The designation Exx refers to the diameter...
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The Edison screw fitting is a system of light bulb connectors, developed by Thomas Edison and licensed starting in 1909 under the Mazda trademark. Most have a right-hand threading, so that it goes in when turned clockwise and comes out when turned counterclockwise, like a hardware screw. There are rare instances where these are reversed to deter theft, so that they cannot be used in other light fixtures.
The designation Exx refers to the diameter in millimeters, even in the U.S., where the bulb glass is listed in eighths of an inch. (For example, E12 has a diameter of 12 mm.) In countries which use 220–240 volts AC domestic power, E27 and E14 are the most common sizes, although the bayonet mount is also used. In 120-volt North America and 100-volt Japan, the standard size for general-purpose lamps is E26. E12 is typically used for candelabra fixtures. E17 is also sometimes used, especially in small table lamps and novelty lighting, and occasionally the lights on newer ceiling fans....
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