Storage tube

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Storage tube

Mostly obsolete, a storage tube is a special monochromatic CRT whose screen has a kind of 'memory' (hence the name): when a portion of the screen is illuminated by the CRT's electron gun

Electron gun

An electron gun is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in televisions and Computer display which use cathode ray tube technology, as well as in other instruments, such as electron microscopes and particle accelerators....
, it stays lit until a screen erase command is given. Thus, screen update commands need only be sent once and this allows the use of a slower data connection, typically serial

Serial communications

In telecommunication and computer science, serial communication is the process of sending data one bit at one time, sequentially, over a communication channel or computer bus....
—a feature very well adapted to computer terminal

Computer terminal

A computer terminal is an electronic or electromechanical computer hardware device that is used for entering data into, and displaying data from, a computer or a computing system....
use in 1960s and 70s computing.

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Mostly obsolete, a storage tube is a special monochromatic CRT whose screen has a kind of 'memory' (hence the name): when a portion of the screen is illuminated by the CRT's electron gun

Electron gun

Serial communications

Computer terminal

Very low bandwidth
Bandwidth

Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a electronic filter, a communication channel, or a signal spectrum, and is typically measured in hertz....
needs compared to vector graphics
Vector graphics

Vector graphics is the use of geometrical Primitive s such as point s, line , curves, and shapes or polygon, which are all based upon mathematical equations, to represent s in computer graphics....
displays, thus allowing much longer cable distances between computer and terminal
No need for display-local RAM
Random-access memory

Random-Assess Memory Card is a form of computer data storage. Today it takes the form of integrated circuits that allows the stored data to be accessed in any order ....
(as in modern terminals), which was prohibitively expensive at the time.

Generally speaking, storage tubes could be divided into two categories. In the more common category, they were only capable of storing "binary

Binary numeral system

The binary numeral system, or notation with a radix of 2. Owing to its straightforward implementation in digital electronic circuitry using logic gates, the binary system is used internally by all modern computers....
" images; any given point on the screen was either illuminated or dark. The Tektronix Direct-View Bistable Storage Tube

DVBST

DVBST was an acronym used by Tektronix to describe their line of "Direct-View Bistable Storage Tubes". These were cathode ray tubes that stored information written to them using an analog technique inherent in the CRT and based upon the secondary emission of electrons from the phosphor screen itself....
was perhaps the most-famous example in this category. Other storage tubes were able to store greyscale/halftone

Halftone

Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size or in spacing. 'Halftone' can also be used to refer specifically to the image that is produced by this process....
d images; the tradeoff was usually a much-reduced storage time.

Two pioneering storage tube displays were MIT Project MAC's ARDS (Advanced Remote Display Station) which used a Tektronix type 611 storage display unit and Tektronix's 4014

Tektronix 4014

Tektronix' 4000 series was a family of text and graphics computer terminals based on the company's storage tube technology. No additional electronics were needed to maintain the display, so the 4000 series were less expensive than earlier graphics terminals and became widely used in the computer aided design market in the 1970s and 80s....
terminal, the latter becoming a de facto

De facto

De facto is a Latin expression that means "concerning the fact" or in practice but not necessarily ordained by law. It is commonly used in contrast to de jure when referring to matters of law, governance, or technique that are found in the common experience as created or developed without or contrary to a regulation....
computer terminal standard some time after its introduction (later being emulated by other systems due to this status).

Storage tube

See also