IBM Selectric
IBM and Remington Rand electric typewriters were the leading models until IBM introduced the IBM Selectric typewriter in 1961, which replaced the typebars with a spherical element (or typeball) slightly smaller than a golf ball, with reverse-image letters molded into 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 previous designs using a platen-carrying carriage moving the paper across a stationary print position.
Due to the physical similarity, the typeball was sometimes referred to as a "golfball". The typeball design had many advantages, especially the elimination of "jams" (when more than one key was struck at once and the typebars became entangled) and in the ability to change the typeball, allowing multiple fonts to be used in a single document.
The IBM Selectric became a commercial success, dominating the office typewriter market for at least two decades. IBM also gained an advantage by marketing more heavily to schools than did Remington, with the idea that students who learned to type on a Selectric would later choose IBM typewriters over the competition in the workplace as businesses replaced their old manual models. By the 1970s, IBM had succeeded in establishing the Selectric as the de facto standard typewriter in mid- to high-end office environments, replacing the raucous "clack" of older typebar machines with the quieter sound of gyrating typeballs.
Later models of IBM Executives and Selectrics replaced inked fabric ribbons with "carbon film" ribbons that had a dry black or colored powder on a clear plastic tape. These could be used only once, but later models used a cartridge that was simple to replace. A side effect of this technology was that the text typed on the machine could be easily read from the used ribbon, raising issues where the machines were used for preparing classified documents (ribbons had to be accounted for to ensure that typists did not carry them from the facility).
A variation known as "Correcting Selectrics" introduced a correction feature, where a sticky tape in front of the carbon film ribbon could remove the black-powdered image of a typed character, eliminating the need for little bottles of white dab-on correction fluid and for hard erasers that could tear the paper. These machines also introduced selectable "pitch" so that the typewriter could be switched between pica type (10 characters per inch) and elite type (12 per inch), even within one document. Even so, all Selectrics were monospaced—each character and letterspace was allotted the same width on the page, from a capital "W" to a period. Although IBM had produced a successful typebar-based machine with five levels of proportional spacing, called the IBM Executive, proportional spacing was not provided with the Selectric typewriter or its successors the Selectric II and Selectric III.
The only fully electromechanical Selectric Typewriter with fully proportional spacing and which used a Selectric type element was the expensive Selectric Composer, which was capable of right-margin justification and was considered a typesetting machine rather than a typewriter.
In addition to its electronic successors, the Magnetic Tape Selectric Composer (MT/SC), the Mag Card Selectric Composer, and the Electronic Selectric Composer, IBM also made electronic typewriters with proportional spacing using the Selectric element that were considered typewriters or word processors instead of typesetting machines.
The first of these was the relatively obscure Mag Card Executive, which used 88-character elements. Later, some of the same typestyles used for it were used on the 96-character elements used on the IBM Electronic Typewriter 50 and the later models 65 and 85.
By 1970, as offset printing began to replace letterpress printing, the Composer would be adapted as the output unit for a typesetting system. The system included a computer-driven input station to capture the key strokes on magnetic tape and insert the operator's format commands, and a Composer unit to read the tape and produce the formatted text for photo reproduction.
Selectric mechanisms were widely incorporated into computer terminals in the 1960s and 1970s, as they possessed obvious advantages:
- reasonably fast, jam-free, and reliable
- relatively quiet, and more importantly, free of major vibrations
- could produce high quality lower- and upper-case output, compared to competitors such as Teletype machines
- could be activated by a short, low-force mechanical action, allowing easier interfacing to electronic controls
- did not require the movement of a heavy "type basket" to shift between lower- and upper-case, allowing higher speed without heavy impacts
- did not require the platen roller assembly to move from side to side (a problem with continuous-feed paper used for automated printing)
The IBM 2741 terminal was a popular example of a Selectric-based computer terminal, and similar mechanisms were employed as the console devices for many IBM System/360 computers. These mechanisms used "ruggedized" designs compared to those in standard office typewriters.
Read more about this topic: Typewritten, History, Electric Designs