Typewriter

A typewriter is a mechanical, electromechanical, or electronic device with a set of "keys" that, when pressed, cause characters to be printed on a document, usually paper.

Electric designs

Electrical typewriter designs removed the direct mechanical connection between the keys and the element that struck the paper. Nevertheless, up to the 1980s, electric typewriters could be better described as "power-assisted typewriters." They contained only a single electrical component in them, the motor. Where the keystroke had previously moved a typebar directly, now it engaged mechanical linkages that directed mechanical power from the motor into the typebar. This was also true of the forthcoming IBM Selectric.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

IBM and Remington electric typewriters were the leading models until IBM introduced the IBM Selectric typewriter, which replaced the typebars with a spherical typeball (more correctly, "element"), slightly smaller than a golf ball, with the letters molded on its surface. The Selectric used a system of latches, metal tapes, and pulleys driven by an electric motor to rotate the ball into the correct position and then strike it against the ribbon and platen. The typeball moved laterally in front of the paper instead of the former platen-carrying carriage moving the paper across a stationary print position.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The typeball design had many advantages, especially in eliminating of "jams" when more than one key was struck at once, and in the ability to change the typeball, allowing multiple fonts to be used in a single document. Selectric mechanisms were widely incorporated into computer terminals in the 1970s, because the typing mechanism was fast and jam-free; could be initiated by a short, low-force mechanical action; and did not require the movement of a heavy "type basket" in order to shift between lower- and upper-case.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Later models of Selectrics replaced inked fabric ribbons with "carbon film" ribbons that had a dry black or colored powder on a "once-thru" clear plastic tape. These could be used only once but they were in a cartridge that was simple to replace. They also introduced auto-correction, where a sticky tape in front of the print ribbon could remove the black-powdered image of a typed character, and introduced selectable "pitch" so that the typewriter could be switched among pica ("10 pitch"), elite ("12 pitch"), and sometimes agate ("15 pitch"), even in one document. Even so, all Selectrics were monospaced -- each and every character was the same width. Although IBM had produced a successful typebar-based machine, the IBM Executive, with proportional spacing, no proportionally spaced Selectric office typewriter was ever introduced. There was, however, a much more expensive proportionally spaced machine called the Selectric Composer which was considered a typesetting machine rather than a typewriter.

Related Topics:
Monospaced - IBM Executive - Selectric Composer

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The final major development of the typewriter was the "electronic" typewriter. Most of these replaced the typeball with a daisy wheel mechanism (a disk with the letters molded on the outside edge of the "petals"). A plastic daisy-wheel was much simpler and cheaper than the typeball but wore out more easily. Some electronic typewriters were in essence dedicated word processors with internal memory and cartridge or diskette external memory-storage devices. Unlike the Selectrics and earlier models, these really were "electronic" and relied on integrated circuits and multiple electromechanical components.

Related Topics:
Daisy wheel - Word processor

~ ~ ~ ~ ~ ~ ~ ~ ~ ~