IBM Selectric Typewriter

The IBM Selectric typewriter was a highly successful model line of electric typewriters introduced by IBM on July 31, 1961.

Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a traditional typewriter, the Selectric had a type element (frequently called a "typeball", or even more informally, a "golf ball") that rotated and pivoted to the correct position before striking. The type element could be easily changed so as to print different fonts in the same document, resurrecting a capacity that had been pioneered by the Blickensderfer typewriter sixty years before. The Selectric also replaced the traditional typewriter's moving carriage with a paper roller ("platen") that stayed in position while the typeball and ribbon mechanism moved from side to side.

The Selectric mechanism was notable for using internal mechanical binary coding and two mechanical binary-digital-to-analog converters, called whiffletree linkages, to select the character to be typed.

Selectrics and their descendants eventually captured 75 percent of the United States market for electric typewriters used in business. IBM replaced the Selectric line with the IBM Wheelwriter in 1984 and transferred its typewriter business to the newly formed Lexmark in 1991.