Letter-quality printer

A letter-quality printer was a form of computer impact printer that was able to print with the quality typically expected from a business typewriter such as an IBM Selectric.

A letter-quality printer operates in much the same fashion as a typewriter. A metal or plastic printwheel embossed with letters, numbers, or symbols strikes an inked ribbon, depositing the ink (or carbon, if an expensive single-strike ribbon was installed) on the page and thus printing a character.

Over time, several different technologies were developed including automating ordinary typebar typewriter mechanisms (such as the Friden Flexowriter), daisy wheel printers (dating from a 1939 patent, but brought to life in the 1970s by Diablo engineer David S. Lee) where the type is moulded around the edge of a wheel, and "golf ball" (the popular informal name for "typeball", as used in the IBM Selectric typewriter) printers where the type is distributed over the face of a globe-shaped printhead (including automating IBM Selectric mechanisms such as the IBM 2741 terminal). The daisy wheel and Selectric-based printers offered the advantage that the typeface was readily changeable by the user to accommodate varying needs.

These printers were referred to as "letter-quality printers" during their heyday, and could produce text which was as clear and crisp as a typewriter (though they were nowhere near the quality of printing presses). Most were available either as complete computer terminals with keyboards (or with a keyboard add-on option) that could double as a typewriter in stand-alone ("off-line") mode, or as print-only devices. Because of its low cost at the time, the daisy wheel printer became the most successful, the method used by Diablo, Qume, Brother and Apple.

Letter-quality impact printers, however, were slow, noisy, incapable of printing graphics or images (unless the programmable microspacing and over-use of the dot were employed), sometimes limited to monochrome, and limited to a fixed set (usually one) of typefaces without operator intervention, though certain font effects like underlining and boldface could be achieved by overstriking. Soon, dot-matrix printers (such as the Oki Microline 84) would offer "Near Letter Quality (NLQ) modes which were much faster than daisy-wheel printers, could produce graphics well, but were still very noticeably lower than "letter quality". Nowadays, printers using non-impact printing (for example laser printers, inkjet printers, and other similar means) have replaced traditional letter-quality printers in most applications. The quality of inkjet printers can approach the old letter-quality impact printers (but can be limited by factors such as paper type).

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