Telegraph code
Encyclopedia
A telegraph code is a character encoding
used to transmit information
through telegraphy
machines. The most famous such code is Morse code
.
It encodes each letter of the alphabet as a series of dots and dashes. International Code developed from Morse's original listing and makes a binary code. The speed of sending is directly related to the length of the shortest (dot) element: a dash is three dots long, an inter-character gap is the same (3 dots) long, and inter-word and sentence gaps should be 5 or 7 dots long (change from earlier standard - 5 dots). The speed of sending is also referred to as words per minute, and is classically based on the 'paris' formula - as 'paris' is considered to be an average length word. See main article on Morse Code
.
Morse code can even be used to transmit Chinese character
s.
There already existed dictionaries
which numbered the Chinese characters. It is simply a case of sending the numbers by Morse Code, and these numbers are then looked up in the dictionary at the receiving end.
In practice, this is a slow process, unless done by an expert Chinese telegrapher who can remember all the numbers of the approximately 5,000 characters in common use.
s to allow typed messages to be transmitted and received without Morse code training.
At the time, hardware costs depended on the length of the longest code.
With an alphabet of 26 uppercase letters, the code had to be at least 5 bits long.
To reduce hardware cost, teleprinter manufacturers adopted the fixed-length 5 bit Baudot code
(rather than trying to use variable-length Morse code).
Users were not satisfied with the limited character set available in Baudot code. Demand for lowercase letters and more punctuation marks led to teleprinters with a 6-bit TeleTypeSetter (TTS) code, and later, 7-bit ASCII
code.
(Demand for accented vowels led to the 8-bit
ISO 8859-1. Demand for Cyrillic, Hebrew, Arabic, Greek, and other letters led to many variations of ISO 8859. Demand for using more than one of these sets of letters at the same time led to the 16 bit Unicode
. Demand for Chinese characters led to 20-bit Unicode
, which clearly is impossible for any typewriter
like formed character mechanical teleprinter, although dot-matrix printers can print Chinese characters.)
, originally created for ship communication by signalling using flags, was expanded by adding a collection of five-letter codes to be used by radiotelegraph operators.
Character encoding
A character encoding system consists of a code that pairs each character from a given repertoire with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the transmission of data through telecommunication networks or storage of text in...
used to transmit information
Information
Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
through telegraphy
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
machines. The most famous such code is Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
.
Manual telegraph codes
Morse code can be transmitted and received with very primitive equipment.It encodes each letter of the alphabet as a series of dots and dashes. International Code developed from Morse's original listing and makes a binary code. The speed of sending is directly related to the length of the shortest (dot) element: a dash is three dots long, an inter-character gap is the same (3 dots) long, and inter-word and sentence gaps should be 5 or 7 dots long (change from earlier standard - 5 dots). The speed of sending is also referred to as words per minute, and is classically based on the 'paris' formula - as 'paris' is considered to be an average length word. See main article on Morse Code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
.
Morse code can even be used to transmit Chinese character
Chinese character
Chinese characters are logograms used in the writing of Chinese and Japanese , less frequently Korean , formerly Vietnamese , or other languages...
s.
There already existed dictionaries
Chinese telegraph code
The Chinese Telegraph Code, Chinese Telegraphic Code, or Chinese Commercial Code is a four-digit decimal code for electrically telegraphing messages written with Chinese characters.- Encoding and decoding :...
which numbered the Chinese characters. It is simply a case of sending the numbers by Morse Code, and these numbers are then looked up in the dictionary at the receiving end.
In practice, this is a slow process, unless done by an expert Chinese telegrapher who can remember all the numbers of the approximately 5,000 characters in common use.
Automatic telegraph codes
Manufacturers developed teleprinterTeleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
s to allow typed messages to be transmitted and received without Morse code training.
At the time, hardware costs depended on the length of the longest code.
With an alphabet of 26 uppercase letters, the code had to be at least 5 bits long.
To reduce hardware cost, teleprinter manufacturers adopted the fixed-length 5 bit Baudot code
Baudot code
The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII. It was the predecessor to the International Telegraph Alphabet No 2 , the teleprinter code in use until the advent of ASCII. Each character in the alphabet is represented by a series of bits, sent over a...
(rather than trying to use variable-length Morse code).
Users were not satisfied with the limited character set available in Baudot code. Demand for lowercase letters and more punctuation marks led to teleprinters with a 6-bit TeleTypeSetter (TTS) code, and later, 7-bit ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
code.
(Demand for accented vowels led to the 8-bit
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
ISO 8859-1. Demand for Cyrillic, Hebrew, Arabic, Greek, and other letters led to many variations of ISO 8859. Demand for using more than one of these sets of letters at the same time led to the 16 bit Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
. Demand for Chinese characters led to 20-bit Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
, which clearly is impossible for any typewriter
Typewriter
A typewriter is a mechanical or electromechanical device with keys that, when pressed, cause characters to be printed on a medium, usually paper. Typically one character is printed per keypress, and the machine prints the characters by making ink impressions of type elements similar to the pieces...
like formed character mechanical teleprinter, although dot-matrix printers can print Chinese characters.)
International Code of Signals (radiotelegraph)
In 1931, the International Code of SignalsInternational Code of Signals
The International Code of Signals is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters. Signals can be sent by flaghoist, signal lamp , flag semaphore, radiotelegraphy, and radiotelephony...
, originally created for ship communication by signalling using flags, was expanded by adding a collection of five-letter codes to be used by radiotelegraph operators.
See also
- Commercial codeCommercial codeCommercial code might refer to:*Commercial code , a set of laws designed to regulate comemrce*Commercial code , a code used in telegraph and telex messages....
- Chinese telegraph codeChinese telegraph codeThe Chinese Telegraph Code, Chinese Telegraphic Code, or Chinese Commercial Code is a four-digit decimal code for electrically telegraphing messages written with Chinese characters.- Encoding and decoding :...
- Great Western Railway telegraphic codesGreat Western Railway telegraphic codesGreat Western Railway telegraphic codes were a commercial telegraph code used to shorten the telegraphic messages sent between the stations and offices of the railway....