Braille
The braille system, devised in 1821 by Frenchman Louis Braille, is a method that is widely used by blind people to read and write. Each braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each. A dot may be raised at any of the six positions to form sixty-four (26) combinations, including the combination in which no dots are raised. For reference purposes, a particular combination may be described by naming the positions where dots are raised, the positions being universally numbered 1 to 3, from top to bottom, on the left, and 4 to 6, from top to bottom, on the right. For example, dots 1-3-4 would describe a cell with three dots raised, at the top and bottom in the left column and on top of the right column, i.e., the letter m. In braille, pages are separated by a line so that you can feel going across the page.
The braille system, devised in 1821 by Frenchman Louis Braille, is a method that is widely used by blind people to read and write. Each braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each. A dot may be raised at any of the six positions to form sixty-four (26) combinations, including the combination in which no dots are raised. For reference purposes, a particular combination may be described by naming the positions where dots are raised, the positions being universally numbered 1 to 3, from top to bottom, on the left, and 4 to 6, from top to bottom, on the right. For example, dots 1-3-4 would describe a cell with three dots raised, at the top and bottom in the left column and on top of the right column, i.e., the letter m. In braille, pages are separated by a line so that you can feel going across the page.
The braille system was based on a method of communication originally developed by Charles Barbier in response to Napoleon's demand for a code that soldiers could use to communicate silently and without light at night called night writing. Barbier's system was too complex for soldiers to learn, and was rejected by the military; in 1821 he visited the National Institute for the Blind in Paris, France, where he met Louis Braille. Braille identified the major failing of the code, which was that the human finger could not encompass the whole symbol without moving, and so could not move rapidly from one symbol to another. His modification was to use a 6 dot cell — the braille system — which revolutionized written communication for the blind
The Braille alphabet
Braille can be seen as the world's first binary encoding scheme for representing the characters of a writing system. The system as originally invented by Braille consists of two parts:
1. A character encoding for mapping characters of the French language to tuples of six bits or dots.
2. A way of representing six-bit characters as raised dots in a Braille cell.
Today different braille codes (or code pages) are used to map character sets of different languages to the six bit cells. Different braille codes are also used for different uses like mathematics and music. However, because the six-dot Braille cell only offers 64 possible combinations, of which some are omitted because they feel the same (having the same dots pattern in a different position), many Braille characters have different meanings based on their context. Therefore, character mapping is not one-to-one.
In addition to simple encoding, modern braille transcription uses contractions to increase reading speed.
Braille cell
Braille generally consists of cells of 6 raised dots arranged in a grid of two dots horizontally by three dots vertically. The dots are conventionally numbered 1, 2, and 3 from the top of the leftward column and 4, 5, and 6 from the top of the rightward column.
The presence or absence of dots gives the coding for the symbol. Dot height is approximately 0.02 inches (0.5 mm); the horizontal and vertical spacing between dot centers within a braille cell is approximately 0.1 inches (2.5 mm); the blank space between dots on adjacent cells is approximately 0.15 inches (3.75 mm) horizontally and 0.2 inches (5.0 mm) vertically. A standard braille page is 11 inches by 11.5 inches and typically has a maximum of 40 to 43 Braille cells per line and 25 lines.
Large Cell Braille
Large Cell Braille, or more commonly "Jumbo Braille", is an alternate way of writing Braille. The dot combinations are the same as those used in traditional Braille, except that the spacing between dots and cells is increased somewhat. The dots themselves are the same size as dots in standard Braille.
Large Cell Braille is used by those who have difficulty feeling standard Braille.
Encoding
As originally conceived by Louis Braill
e, a sequence of characters, using the top 4 dots of the braille cell, represents letters a through j. Dot 3 is added to each of the a through j symbols to give letters k through t. Both of the bottom dots (dots 3 and 6) are added to the symbols for "a" through e to give letters u, v, x, y, and z. The letter w is an exception to the pattern because French did not make use of the letter "w" at the time Louis Braille devised his alphabet, and thus he had no need to encode the letter "w".English Braille codes the letters and punctuation, and some double letter signs and word signs directly, but capitalization and numbers are dealt with by using a prefix symbol. In practice, Braille produced in the United Kingdom does not have capital letters.
There are Braille codes for representing shorthand (produced on a machine which embosses a paper tape) and for representing mathematics (Nemeth Braille) and musical notation (Braille music).
Writing Braille
Braille may be produced using a slate and a stylus in which each dot is created from the back of the page, writing in mirror image, by hand, or it may be produced on a Braille typewriter or Perkins Braille, or produced by a Braille embosser attached to a computer. It may also be rendered using a refreshable Braille display.
Braille has been extended to an 8-dot code, particularly for use with Braille embossers and refreshable Braille displays. In 8-dot Braille the additional dots are added at the bottom of the cell, giving a matrix 4 dots high by 2 dots wide. The additional dots are given the numbers 7 (for the lower-left dot) and 8 (for the lower-right dot). 8-dot braille has the advantages that the case of an individual letter is directly coded in the cell containing the letter and that all the printable ASCII characters can be represented in a single cell. All 256 (28) possible combinations of 8 dots are encoded by the Unicode standard. Braille with six dots is frequently stored as Braille ASCII.
Braille transcription
Although it is possible to transcribe Braille by simply substituting the equivalent Braille character for its printed equivalent, such a character-by-character transcription (known as Grade 1 Braille) is used only by beginners.
Braille characters are much larger than their printed equivalents, and the standard 11" by 11.5" (28 cm × 30 cm) page has room for only 25 lines of 43 characters. To reduce space and increase reading speed, virtually all Braille books are transcribed in what is known as Grade 2 Braille, which uses a system of contractions to reduce space and speed the process of reading. As with most human linguistic activities, Grade 2 Braille embodies a complex system of customs, styles, and practices. The Library of Congress's Instruction Manual for Braille Transcribing runs to nearly 200 pages. Braille transcription is skilled work, and Braille transcribers need to pass certification tests.
In English, the system of Grade 2 Braille contractions begins with a set of 23 words which are contracted to single characters. Thus the word but is contracted to the single letter b, can to c, do to d, and so on. Even this simple rule creates issues requiring special cases; for example, d is, specifically, an abbreviation of the verb do; the noun do representing the note of the musical scale is a different word, and must be spelled out.
Portions of words may be contracted, and many rules govern this process. For example, the character with dots 2-3-5 (the letter "f" lowered in the braille cell) stands for "ff" when used in the middle of a word. At the beginning of a word, this same character stands for the word "to" although the character is written in braille with no space following it. At the end of a word, the same character represents an exclamation point.
The contraction rules take into account the linguistic structure of the word; thus, contractions are not to be used when their use would alter the usual Braille form of a base word to which a prefix or suffix has been added. And some portions of the transcription rules are not fully codified and rely on the judgment of the transcriber. Thus, when the contraction rules permit the same word in more than one way, preference is given to "the contraction that more nearly approximates correct pronunciation."
Grade 3 Braille is a system that includes many additional contractions, almost shorthand; it is not used for publication, but is used mostly for individuals for their personal convenience.
The current series of Canadian banknotes have raised dots on the banknotes that indicate the denomination and can be easily identified by visually impaired people; this 'tactile feature' does not use standard Braille but, instead, a system developed in consultation with blind and visually impaired Canadians after research indicated that not all potential users read Braille.
