IBM Selectric typewriter
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The IBM Selectric typewriter (occasionally known as the IBM Golfball typewriter) is the electric typewriter design that brought the typewriter into the electronic age starting in 1961.
Features
The ability to change fonts, combined with the neat regular appearance of the typed page, was revolutionary and marked the beginning of desktop publishing. Later models with selective pitch and built-in correcting tape carried the trend even further. Any typist could produce a polished manuscript. By 1966, a full typesetting version with justification and proportional spacing was released.The machine had a key lockout feature called "Stroke Storage" that smoothed out the irregular finger strokes of the typist. When a key was pressed a narrow metal tab on the corresponding interposer was pushed down into a slotted tube, called the Selector Compensator, full of ball-bearings under the keyboard. These balls were adjusted to have enough horizontal space for only one interposer tab to enter at a time. The typist could press two keys virtually simultaneously and both characters would print once each in rapid succession. Trying to press three or more keys simultaneously resulted in all the keys being blocked from their full downward travel and no characters typed. At the end of each cycle, the active interposer was pushed forward withdrawing its tab from the Selector Compensator and allowing another interposer's tab to descend. This gave some users the impression that there was a storage buffer. (See typeahead for more information.)
The resulting keyboard feel, with its precise "breakover" tactile feedback at the moment the key was engaged but with some key travel still available before bottoming out, was highly praised by typists. A similar design was used on IBM's model 029 and 129 keypunch machines. Some computer keyboards such as the IBM Model M series and the Northgate "Omnikey" series have attempted to provide a similar tactile feedback, though none use anything like the Selector Compensator working among multiple keys.
Two keys – the Spacebar and the Dash (or Minus)/Underline would repeat at full mechanism speed if held down firmly. This feature was referred to as "Typamatic."
The Selectric as Computer Terminal
Due to their speed (14.8 characters per second), immunity to clashing typebars, trouble-free paper path, high quality printed output, and reliability, Selectric-based mechanisms were also widely used as terminals for computers, replacing both Teletypes and older typebar-based output devices. One popular example was the IBM 2741 terminal, which figured prominently in the early years of the APL programming language. Similar machines such as the IBM 1050 series were used as the console printers for many computers, such as the IBM 1130 and the IBM System/360 series.Despite appearances, these machines were not simply Selectric typewriters with an RS-232 connector added. A Selectric is a marvel of mechanical and production—but not electronic—engineering. As with other electric typewriters, and electric adding machines of the era, Selectrics are best thought of as electromechanical devices: The only electric components are the power cord, power switch, and electric motor. The electric motor runs continuously. The keys are not electrical pushbuttons, as they are on a computer keyboard. Pressing a key does not produce an electrical signal, but rather engages a series of clutches which couple the motor power to the mechanism to turn and tilt the element. A Selectric would work equally well if hand-cranked at sufficient speed.
Adapting this mechanism to the needs of computer input/output was therefore nontrivial. The keyboard and printing mechanism were mechanically separated (keystrokes do not necessarily result in immediate printing), microswitches were added to the keyboard, solenoids were added to allow the computer to trigger the typing mechanism, and interface electronics were needed. Several mechanical components, in particular the motor and the main clutch, had to be upgraded from the typewriter versions to reliably support continuous operation.
The IBM 2741 came in two different varieties, some using "correspondence coding" and the others using what was referred to as "PTT/BCD coding." These referred to the positioning of the characters around the typeball and, therefore, the tilt/rotate codes that had to be applied to the mechanism and sent over the communications link. A "correspondence coding" machine could use type elements from a standard office Selectric. "PTT/BCD coding" machines needed special elements, and did not have as wide a variety of fonts available. The IBM 1050 and its derivatives were only available in PTT/BCD coding, so a type element from, say, a System/360 console printer would produce gibberish on an office Selectric.
IBM introduced several office products using these computer-controlled Selectric mechanisms, beginning with the "Magnetic Tape Selectric Typewriter," or "MT/ST" for short.
Selectric-based computer printers were gradually replaced in favor of printers using a daisy wheel mechanism, such as the Diablo 630.
Design
The Selectric typewriter was first introduced 1961-07-31 and is generally considered to be a design classic. Its industrial design is credited to Eliot Noyes, an influential American designer. Noyes had worked on a number of design projects for IBM; prior to his work on the Selectric, he had been commissioned in 1956 by Thomas Watson to create IBM's first house style -- indeed, these influential efforts, in which Noyes collaborated with Paul Rand, Marcel Breuer, and Charles Eames, have been referred to as the first "house style" program in American business.After the Selectric II was introduced a few years later, the original design was designated the Selectric I. The Correcting Selectric II differed from the Selectric I in many respects:
- The Selectric II was squarer at the corners, whereas the Selectric I was rounder.
- The Selectric II had a Dual Pitch option to allow it to be switched (with a lever at the top left of the "carriage") between 10 and 12 characters per inch, whereas the Selectric I had one fixed "pitch".
- The Selectric II had a lever (at the top left of the "carriage") (option available only on dual pitch models) that allowed characters to be shifted up to a half space to the left (for inserting a word one character longer or shorter in place of a deleted mistake), whereas the Selectric I did not.
- The Selectric II had optional auto-correction (with the extra key at the bottom right of the keyboard), whereas the Selectric I did not. This worked in conjunction with a correction ribbon: Either the transparent and slightly adhesive "Lift-Off" tape (for use with Correctable Film ribbons), or the white "Cover-Up" tape (for cloth or Tech-3 ribbons). The white or transparent correction tape was at the left of the typeball and its orange take-up spool at the right of the typeball, and was changed independently from the typing ribbon. The correction key backspaced the carriage by one space and also put the machine in a mode wherein the next character typed would use the correction tape instead of the normal ribbon, and furthermore would not advance the carriage. The typist would press the correction key and then re-type the erroneous character, either lifting it off of the page or covering it with white-out powder, then type the correct character. Any number of mistakes could be corrected this way, but the process was entirely manual, as the machine had no memory of the typed characters.
- The Selectric II had a lever (above the right platen knob) that would allow the platen to be turned freely but return to the same vertical line whereas the Selectric I has the same feature, but with a different lever design. This feature is found on almost every typewriter, manual or electric. It can be used for typing super- or subscripts, although accurate alignment is difficult.
- A Selectric I had to be ordered to use either cloth reusable ribbon or one-time carbon film ribbon; the same machine could not use both. The Correcting Selectric II used a new ribbon cartridge technology consisting of wider ribbons that give more typed characters per inch of ribbon. Successive characters were staggered vertically on the ribbon, which incremented less than a full character position each time as a result. Any Correcting Selectric II could use any of three types of ribbon, which all came in similar-looking cartridges: Reusable cloth ribbon with associated Cover-Up tape; Correctable (carbon) Film ribbon with associated Lift-Off tape; and the Tech-3 permanent ribbon, introduced later, which used the same Cover-Up tape as the earlier cloth ribbon. The Tech-3 ribbon essentially replaced the cloth ribbon, as they offered similar typing quality to the film ribbon but at a cost comparable to the reusable cloth. Tech-3 ribbons provided much higher security and longer life than the Correctable Film ribbon. Like the cloth ribbon, Tech-3 ribbons incremented only a fraction of the character width after being struck. Unlike the cloth ribbon, the Tech-3 ribbon provided high quality impressions for several characters from each spot on the one-time-use ribbon. Because characters overstrike each other on a Tech-3 ribbon several times it could not be easily read to discover what had been typed. In addition, where the Correctable Film ribbon was unsuitable for documents such as checks due to the ease of lifting the ink from the document, the Tech-3 ribbon's impressions were permanent as soon as they were struck. Some colored ribbons (e.g. brown) were also available.
In 1966, IBM released the Selectric Composer, the first desktop publishing system. The hybrid typewriter produced camera-ready justified copy using proportional fonts in a number of font sizes and styles, using the typeball. The machine required that material be typed twice. The first time was to measure the length of the line and count the spaces, recording special measurements on the right margin. The second time it was typed, the operator used the measurements to set justification for the line. The elements for the Selectric Composer would fit on a Selectric, and vice versa, but they could not actually be used on each other's machines: the characters were arranged differently around the element and were also positioned differently within each character area. Selectric Composer elements can be identified by a colored index arrow (the color is used to set a median character width on the machine) and a cryptic series of letters and numbers identifying the font, size, and variation, for example "UN-11-B" for Univers 11 point bold.
In 1964 IBM introduced the "Magnetic Tape Selectric Typewriter;" in 1967, a "Mag Tape Selectric Composer", and in 1969, a "Magnetic Card Selectric Typewriter." These featured computer-interfaced typing mechanisms and a magnetic storage device for recording, editing, and replaying typed material. These machines were among the first to provide word processing capability in any form.
In the 1980s IBM introduced a Selectric III and several other Selectric models, some of them word processors or type-setters instead of typewriters, but by then the rest of the industry had caught up with the trend, and IBM's new models did not dominate the market the way the first Selectric had. The Selectric III features a 96 character element vs. the previous 88 character element. IBM's series of "Electronic Typewriters" used this same 96 character element. The 96 character elements can be identified by yellow printing on the top plastic surface and the legend "96," which always appears along with the font name and pitch. The 96 and 88 character elements are mechanically incompatible with each other, and 96 character elements were not available in as many fonts as the older 88 character types. Most Selectric IIIs and Electronic Typewriters only had keys for 92 printable characters; the 96 character keyboard was an optional feature. Fitting the additional keys onto the keyboard required shrinking of the Return key and this was annoying to many typists, so it was not the default configuration. The keytops on the Selectric III and Electronic Typewriters were larger and more square than those on earlier Selectrics.
Elements and Fonts
Some of the interchangeable font elements available for the Selectric models included:Small (12-pitch) fonts
- Elite 72
- Auto Elite
- Large Elite (12)
- Prestige Elite 72
- Prestige Elite 96*
- Adjutant
- Artisan
- Contempo
- Courier (12)
- Courier Italic
- Courier Italic 96*
- Forms
- Letter Gothic
- Letter Gothic 96*
- Light Italic
- OCR
- Olde World
- Oriental
- Report 96 (12)*
- Scribe
- Scribe 96*
- Script
- Symbol
Large (10-pitch) fonts
- Pica 72
- Prestige Pica 72
- Pica 96*
- Advocate
- Boldface
- Bookface Academic 72
- Business Script
- Courier (10)
- Courier 96 (10)
- Bold Courier (10)
- Delegate
- Delegate 96*
- Manifold
- Orator
- Sunshine Orator
- Orator 96*
- Orator Presenter
- Report 96 (10)*
- Title
Selectric Trivia
- Part of the Selectric's design was based on a toy typewriter made by Marx Toys. IBM bought the rights to the design.
- Bob Bemer, known as "the father of ASCII," realized that the Selectric would make a great computer terminal and tried unsuccessfully to get the Selectric element to provide for 64 printing characters per case instead of just 44.
- Capitalizing on the then-new Selectric typewriters, the IBM Pavilion at the 1964 New York World's Fair was a large theater shaped and styled like a very-much over-grown Selectric type element. The audience seating area was lifted up into the type element theater for the presentation.
- Hunter S. Thompson was a well known user of Selectric typewriters.
- A 1963 episode of the Perry Mason TV show, "The Case of the Elusive Element," turned on the fact that the pivoting textball ("element") in Selectric typewriters could easily be switched, making it impossible to know which machine had actually been used to type a message.
- In a 1975 episode of the television show Columbo, "Now You See Him...," Columbo finds evidence of an incriminating document in the carbon film ribbon of a Selectric typewriter.
References
External links
- [History of IBM typewriters]
- [History of typewriter design], featuring the Selectric.
- [Dead medium: the IBM Selectric Typewriter]
- [Selectric Typewriter Museum]
- [The IBM Selectric Composer] desktop typesetting system
- [The IBM Selectric as a computer I/O device] PDF files at Bitsavers.org
- [Bob Bemer's recollections of early Selectric design issues]
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