A refreshable braille display or braille terminal is an electro-mechanical device for displaying

braille Braille (Pronounced: ) is a tactile writing system used by people who are visually impaired, including people who are Blindness, blind, Deafblindness, deafblind or who have low vision. It can be read either on Paper embossing, embossed paper ...

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 Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or Computer hardware, hardware products. A text-to-speech (TTS) system conve ...

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

The base of a refreshable braille display often integrates a pure braille keyboard. Similar to the

Perkins Brailler The Perkins Brailler is a "braille typewriter" with a key corresponding to each of the six dots of the braille code, a space key, a backspace key, and a line space key. Like a manual typewriter, it has two side knobs to advance paper through t ...

, 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 character cells, each of which can raise or lower a combination of eight round-tipped pins. Other variants exist that use a conventional

QWERTY QWERTY () is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on a layout created f ...

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 Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word ''p ...

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 Braille (Pronounced: ) is a tactile writing system used by people who are visually impaired, including people who are blind, deafblind or who have low vision. It can be read either on embossed paper or by using refreshable braille displ ...

s are displayed. Models with between 18 and 40 cells exist in some notetaker devices. On some models the position of the

cursor Cursor may refer to: * Cursor (user interface), an indicator used to show the current position for user interaction on a computer monitor or other display device * Cursor (databases), a control structure that enables traversal over the records in ...

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 A screen reader is a form of assistive technology (AT) that renders text and image content as speech or braille output. Screen readers are essential to people who are blindness, blind, and are useful to people who are visual impairment, visually ...

. It gathers the content of the screen from the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

, 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

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

to help screen readers obtain this information, such as UI Automation (UIA) for

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

VoiceOver Voice-over (also known as off-camera or off-stage commentary) is a production technique where a voice—that is not part of the narrative (non-diegetic)—is used in a radio, television production, filmmaking, theatre, or other presentations. ...

for

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

and

iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...

, and AT-SPI for

GNOME A gnome is a mythological creature and diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus in the 16th century and later adopted by more recent authors including those of modern fantasy literature. Its characte ...

Rotation-wheel Braille display

A rotating-wheel Braille display was developed in 2000 by the

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...

(NIST) and another at the Leuven University in Belgium.Pictures of the experimental setup
/ref> In these units, braille dots are put on the edge of a spinning

wheel A wheel is a circular component that is intended to rotate on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction wi ...

, 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 An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...

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

References

External links