International uniformity of braille alphabets

An early braille chart, displaying the numeric order of the characters

Braille arranged his characters in decades (groups of ten), and assigned the 25 letters of the French alphabet to them in order. The characters beyond the first 25 are the principal source of variation today.

In the first decade, only the top four dots are used; the two supplementary characters have dots only on the right. These patterns are repeated for the second decade, with the addition of a diacritic at dot 3; for the third, at dots 3 and 6; for the fourth, at 6; and for the fifth decade, by duplicating the first decade within the lower four dots.

Braille is in its origin a numeric code. Louis Braille applied the characters in numerical order to the French alphabet in alphabetical order. As braille spread to other languages, the numeric order was retained and applied to the local script. Therefore, where the alphabetical order differed from that of French, the new braille alphabet would be incompatible with French Braille. For example, French was based on a 25-letter alphabet without a w. When braille was adopted for English in the United States, the letters were applied directly to the English alphabet, so that braille letter of French x became English w, French y became English x, French z English y, and French ç English z. In the United Kingdom, however, French Braille was adopted without such reordering. Therefore, any English book published in braille needed to be typeset separately for the United States and the United Kingdom. Similarly, the letters for Egyptian Arabic Braille were assigned their forms based on their nearest French equivalents, so that for example Arabic d had the same braille letters as French d. For Algerian Arabic Braille, however, the braille characters were assigned to the Arabic alphabet according to the Arabic alphabetical order, so that Algerian d was the same character as Egyptian h. Thus an Arabic book published in Algeria was utterly unintelligible to blind Egyptians and vice versa.

In addition, in other alphabets braille characters were assigned to print letters according to frequency, so that the simplest letters would be the most frequent, making the writing of braille significantly more efficient. However, the letter frequencies of German were very different from those of English, so that frequency-based German braille alphabets were utterly alien to readers of frequency-based American Braille, as well as to numerically based German, English, and French Braille.

The 1878 congress, convening representatives from France, Britain, Germany, and Egypt, decided that the original French assignments should be the norm for those countries:

"[Due to] the tendencies in America and Germany to re-arrange the Braille alphabet [to fit their own alphabetical orders], the Congress decided ... that it should be adopted ... with the values of its symbols unaltered from those of the original French."[2]

Gradually the various reordered and frequency-based alphabets fell out of use elsewhere as well.

This decision covered the basic letters of the French alphabet at the time; w had been appended with the extra letters, so the 26 letters of the Basic Latin alphabet are slightly out of numeric order:

a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

p

q

r

s

t

u

v

x

y

z

w

For non-Latin scripts, correspondences are generally based, where possible, on their historical connections or phonetic/transcription values.[3] For example, Greek γ gamma is written ⠛ g, as it is romanized, not ⠉ c, as it is ordered in the alphabet or as it is related historically to the Latin letter c. Occasional assignments are made on other grounds, such as Greek ω omega, which is written ⠺ w, as in beta code and internet chat alphabets, due to the graphic resemblance of Latin w and Greek ω.

In 1929 in Paris, the American Foundation for Overseas Blind sponsored a conference on harmonizing braille among languages which use the Latin script, which had diverged in the previous decades.

When additional letters are needed for a new braille alphabet, several remedies are used.

1. They may be borrowed from an existing alphabet; French–German ⠜ ä, ⠪ ö, and ⠳ ü, for example, are widely used where a language had need of a second a-, o-, or u-vowel. Likewise, the values of English contracted ("Grade 2") ⠡ ch, ⠩ sh, and ⠹ th are widely used for similar sounds in other languages.
2. An otherwise unused letter may be reassigned. For example, Tibetan Braille, which is based on German Braille, reassigns ⠉ c, ⠟ q, ⠭ x, and ⠽ y, which are redundant in German.
3. In the case of diacritics in the print alphabet, a point may be added to the base letter in braille. Latvian Braille, for example, adds dot 6 to indicate a diacritic, at the cost of abandoning several international assignments.
4. New letters may be invented by modifying a similar letter. Modification may be done through moving the letter (thus ⠢ and ⠔ for a second e or i vowel), stretching the letter (again, ⠡ and ⠌ for e- and i-like vowels), or rotating or reflecting it. The latter is quite common, producing such pairs as ⠎ s – ⠱ sh and ⠝ n – ⠫ ny. See Hungarian Braille for an alphabet which has exploited a pattern of mirror images, and Thai Braille for the series ⠧ บ b, ⠯ ป p, ⠏ ผ ph₁, ⠹ พ ph₂.

A regional UNESCO conference on braille uniformity for southern Asia took place in 1950.[12] This led to a conference with global scope the following year. The 1951 congress found many conflicting braille assignments:

"Most Asian and African languages contain more letters or sounds than Roman had equivalents for, [and] they had to find some way of representing them. Most of the designers of Braille spoke English and some of them turned to the contractions of English Braille to find signs which would provide precedents for local letter values ... But beyond these again, many non-European alphabets included letters for which no Braille precedent had been created. Arbitrary signs had to be allotted to them, with the consequence that even throughout these traditional Brailles only limited uniformity was achieved."[13]

The congress recognized the role of English contracted braille in establishing a partial international standard, and recommended that alphabets follow existing conventions as much as possible.

Common extended correspondences

The following assignments include common secondary vowels and consonants: Whenever a second a- or d-based letter is needed in an alphabet, use of the same secondary braille letter is common. Additional alternative letters are used in some braille alphabets. English grade 2 braille correspondences are given below for recognition; these are often the basis of international usage.

Vowels Letter Braille Extended use Notes A Arabic alif 2nd A German Ä Indic Ā Arabic Ā Scandinavian Æ English ar E 2nd E Indic Ĕ African Ẹ, Ɛ English en I 2nd I Indic Ī African Ị English in	Vowels (cont.) Letter Braille Extended use Notes long I (ai) Indic AI O 2nd O French Œ German Ö Indic AU African Ọ, Ɔ English ow U 2nd U German Ü Indic Ū African Ụ English ou
Occlusives Letter Braille Extended use Notes P B T 2nd T Indic Ṭ Arabic Ṭ English with D 2nd D Indic Ḍ Arabic Ḍ African Ɖ English ed C CH Indic CH English ch	Occlusives (cont.) Letter Braille Extended use Notes J K G Q Arabic Q African KW also Indic KṢ apostrophe English apostrophe used for Arabic ء M N NG African Ŋ Indic Ṅ English ing
Fricatives Letter Braille Extended use Notes F V TH Indic TH Arabic Θ English th Icelandic Þ DH Indic DH Arabic/Icelandic Ð English the S 2nd S French Ç Indic Ṣ Arabic Ṣ English and Z	Fricatives (cont.) Letter Braille Extended use Notes SH Indic Ś Arabic Š, African Ṣ, Ʃ English sh ZH Indic JH English was X /x/ or /ks/ Arabic X GH Indic GH African Ɣ Arabic Ɣ English gh H 2nd H Arabic Ħ English wh German SCH Chinese SH
Liquids Letter Braille Extended use Notes L 2nd L Indic Ḷ English world R 2nd R Indic Ṛ or Ṟ English er African Ẹ / Ɛ Y W	Additional consonants[14] Letter Braille Extended use Notes Dh Indic ḌH Arabic Ẓ 2nd Dh braille pattern English for B African Ɓ, GB English bb 2nd B braille pattern K African Ƙ Indic KH German "ck" 2nd K braille pattern English ance ayin Arabic ʿ French "à" English of

• Meeting of the Advisory Committee on Braille Problems, Unesco, 1949
• "World Braille Usage" (2nd ed.). UNESCO. 1990. Retrieved 2012-04-19.