A text display is an electronic

alphanumeric Alphanumericals or alphanumeric characters are any collection of number characters and letters in a certain language. Sometimes such characters may be mistaken one for the other. Merriam-Webster suggests that the term "alphanumeric" may often ...

display device that is mainly or only capable of showing

text Text may refer to: Written word * Text (literary theory) In literary theory, a text is any object that can be "read", whether this object is a work of literature, a street sign, an arrangement of buildings on a city block, or styles of clothi ...

, or extremely limited graphic characters. This includes electromechanical split-flap displays, vane displays, and flip-disc displays; all-electronic

liquid-crystal display A liquid-crystal display (LCD) is a flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liq ...

s, incandescent eggcrate displays, LED displays, and vacuum fluorescent displays; and even electric nixie tubes. There are several ways to form text for display. A segment display uses lines, while a dot-matrix display uses a grid of dots, and both of these are seen in LCD, LED, VFD, and vane/disc types. For split-flap displays, the characters or words are pre-printed, and for nixie tubes the shapes are also pre-formed. In any case, the display elements are controlled by electronics which activate them in the correct physical and temporal sequence to show the desired information. Text displays are used in everything from

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

s ( clock radios, wristwatches) to variable-message signs ( departure boards, intelligent transportation systems), because until the late 2000s, they were (and in many cases still are) the least expensive for their purpose.

Text display types

LED text displays

LED text displays refer to types that are specialized and limited to display of alpha-numeric characters. Most types display either one character or a group of characters. One character is generally displayed by a matrix of LEDs, or by a set of segments.

Liquid-crystal display

(LCD) is a flat panel display, electronic visual display, video display that uses the light modulating or polarizing properties of liquid crystals (LCs). LCs do not emit light directly. A character display type is limited to and specialized for display of alphanumeric characters. They are used in a wide range of applications, including

computer monitor A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a electronic visual display, visual display, support electronics, power supply, Housing (engineering), housing, electri ...

television Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...

, instrument panels, aircraft cockpit displays,

signage Signage is the design or use of signs and symbols to communicate a message. Signage also means signs ''collectively'' or being considered as a group. The term ''signage'' is documented to have been popularized in 1975 to 1980. Signs are any ki ...

, etc. They are common in consumer devices such as video players, gaming devices,

s, watches, calculators, and

telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...

s. The low electrical power consumption of LCDs enables them to be used in battery-powered electronic equipment. It is an electronically modulated optical device made up of any number of

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...

s filled with

liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as i ...

s and arrayed in front of a light source ( backlight) or reflector to produce images in color or monochrome. The earliest discovery leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888. By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units.

Eggcrate displays

An eggcrate display is one older method of displaying an alphanumeric character. It consists of a matrix of incandescent light bulbs. A foam rubber mask with an array of holes surrounding the bulbs is attached to the display, causing it to resemble an egg crate. Some eggcrate displays use a complete 5×7 matrix for each digit, permitting the display of nearly all alphanumeric characters. Other types display only numeric characters and optionally a dollar sign. This type of eggcrate display is popularly used for sports scoreboards. Eggcrate displays have been used on many

game show A game show (or gameshow) is a genre of broadcast viewing entertainment where contestants compete in a game for rewards. The shows are typically directed by a game show host, host, who explains the rules of the program as well as commentating a ...

s to display contestants' scores and/or for countdown clocks because other types of displays, such as LED seven-segment displays, were prone to being washed out by bright studio lights. Though they continued to see extensive use well into the late 1990s, many shows began adopting LCDs in the 2000s. They have also been used as variable-message signs on highways, although they were later superseded by flip-disc, fiber optic, and eventually LED displays.

Vane displays

A vane display is an electro-mechanical type of 7-segment display. Unlike LED and VFD segmented displays, vane displays are composed of seven physical surfaces, typically painted white, but occasionally other colors, such as yellow or fluorescent green. If a segment is to be displayed as "off", it will be rotated so that its edge faces forward, with the painted surface pointing away and not visible. A segment that is to be displayed as "on" will be rotated so that the painted surface is shown.

References