The Baudot Code
The 5-unit (symbol) Baudot code, invented by the French Engineer Emile Baudot in 1870, is an even-length code invented for use in his telegraph multiplexer system. This code was later modified as the 7 ½-unit teleprinter code. Further modification of the Baudot code led to the inventions of the 7-bit ASCII code and the 8-bit EBCIDIC, which are currently used in most computer applications.
Features of the Baudot code
· There are five symbols in each code word.
· All symbols are of equal duration.
· Symbols are denoted by pulses of positive and zero (or negative) voltage levels.
· These voltage levels represent either a 0 or a 1.
· There are 25 (=32) code words in the Baudot code.
· The combinations of symbols include all binary numbers from 00000 to 11111.
· To represent English alphabets, 26 code words are required. Only 6 combinations of symbols are left out and these are insufficient to represent numbers and punctuation marks.
· So, the same combinations are used again with the help of a shift key.
Table 1.15 shows a few examples of Baudot-code words.
Table 1.15 A few examples of the five-unit Baudot code
Letter | Figure | Code word |
A | - | 1 1 0 0 0 |
B | ? | 1 0 0 1 1 |
C | : | 0 1 1 1 0 |
D | $ | 1 0 0 1 0 |
Since telegraph and teleprinter transmissions have become obsolete, the Baudot code is no longer in use in its original 5-unit and 7½-unit forms.