Editing Refreshable braille display

{{Short description|Device for displaying braille characters}}
{{More citations needed|date=September 2019}}
[[File:Plage-braille.jpg|thumb|Refreshable braille display]]
A '''refreshable braille display''' or '''braille terminal''' is an electro-mechanical device for displaying [[braille]] characters, usually by means of round-tipped pins raised through holes in a flat surface. Visually impaired computer users who cannot use a standard computer monitor can use it to read text output. Deafblind computer users may also use refreshable braille displays.

[[Speech synthesizer]]s are also commonly used for the same task, and a blind user may switch between the two systems or use both at the same time depending on circumstances.

==Mechanical details==
[[File:Baum David System 90 (cropped).jpg|thumb|A Baum David System 90 special-purpose computer for the blind, with a braille "screen" and special keyboard]]
The base of a refreshable braille display often integrates a pure braille keyboard. Similar to the [[Perkins Brailler]], the input is performed by two sets of four keys on each side, while output is via a refreshable braille display consisting of a row of electro-mechanical [[braille cell|character cells]], each of which can raise or lower a combination of eight round-tipped pins. Other variants exist that use a conventional [[QWERTY]] keyboard for input and braille pins for output, as well as input-only and output-only devices.

The mechanism which raises the dots uses the [[piezo effect]] of some crystals, whereby they expand when a voltage is applied to them. Such a crystal is connected to a lever, which in turn raises the dot. There has to be a crystal for each dot of the display (''i.e.'', eight per character).

Because of the complexity of producing a reliable display that will cope with daily wear and tear, these displays are expensive. Usually, only 40 or 80 [[braille cell]]s are displayed. Models with between 18 and 40 cells exist in some notetaker devices. 

On some models the position of the [[cursor (computers)|cursor]] is represented by vibrating the dots, and some models have a switch associated with each cell to move the cursor to that cell directly.

==Software==
The software <!--that controls the display is called a [[screen reader]]. It -->gathers the content of the screen from the [[operating system]], converts it into braille characters and sends it to the display.

Screen readers for graphical operating systems are especially complex, because graphical elements like windows or slidebars have to be interpreted and described in text form. Modern operating systems usually have an [[application programming interface|API]] to help screen readers obtain this information, such as [[UI Automation]] (UIA) for [[Microsoft Windows]], [[VoiceOver]] for [[macOS]] and [[iOS]], and [[AT-SPI]] for [[GNOME]].

== Rotation-wheel Braille display ==
A rotating-wheel Braille display was developed in 2000 by the [[National Institute of Standards and Technology]] (NIST) and another at the [[Katholieke Universiteit Leuven|Leuven University]] in Belgium.<ref>{{cite news|
url=https://web.archive.org/web/20131004220126/zdnet.nl/braille/43665/vlaamse-onderzoekster-ontwikkelt-braillecomputermuis| title=Flemish researcher (Tiene Nobels) develops braille computer mouse / Vlaamse onderzoekster (Tiene Nobels) ontwikkelt braillecomputermuis| work=ZDNet}}<br>[https://web.archive.org/web/20070112214727/homes.esat.kuleuven.be/~nobels/braillemuis.html Pictures of the experimental setup]</ref> In these units, braille dots are put on the edge of a spinning [[wheel]], which allows the user to read continuously with a stationary finger while the wheel spins at a selected speed. The braille dots are set in a simple scanning-style fashion as the dots on the wheel spin past a stationary [[actuator]] that sets the braille characters. As a result, manufacturing complexity is greatly reduced and rotating-wheel braille displays, when in actual production, should be less expensive than traditional braille displays.

==Braille e-book==
{{main article|Braille e-book}}

==See also==
* [[GNOME accessibility]]
* [[VoiceOver]]
* [[Tactile (device)|Tactile project at MIT]]

==References==
{{reflist}}

==<span lang="Español" dir="ltr">External</span> links==
*{{webarchive |url=https://web.archive.org/web/20091231121047/http://www.nist.gov/public_affairs/gallery/braille.htm |date=December 31, 2009 |title=NIST: Converting Digital Information to Braille }}
*Information on Bi-directional Refreshable Tactile Display US Patent 6,692,255 

{{Braille}}{{Authority control}}
[[Category:American inventions]]
[[Category:Computer accessibility]]
[[Category:Braille technology]]
[[Category:Haptic technology]]