Baudot code Murray code



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  • baud

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 (ITA2), 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 communication channel such as a telegraph wire or a radio signal. The symbol rate measurement is known as baud, and is derived from the same name.

Baudot code

  • Technically, five bit codes began in the 16th century, when Francis Bacon developed the cipher now called Bacon's cipher. However, this cipher is not a machine cipher and as such is not readily suitable for telecommunications.

Baudot code

  • Baudot invented his original code in 1870 and patented it in 1874. It was a 5-bit code, with equal on and off intervals, which allowed telegraph transmission of the Roman alphabet and punctuation and control signals. It was based on an earlier code developed by Carl Friedrich Gauss and Wilhelm Weber in 1834.

Baudot code

  • Baudot's original code was adapted to be sent from a manual keyboard, and no teleprinter equipment was ever constructed that used it in its original form

Baudot code

  • The table above "shows the allocation of the Baudot code which was employed in the British Post Office for continental and inland services

Baudot code

  • Baudot's code became known as International Telegraph Alphabet No. 1, and is no longer used.

Baudot code Murray code

  • In 1901 Baudot's code was modified by Donald Murray (1865–1945), prompted by his development of a typewriter-like keyboard

Baudot code Murray code

  • The Murray code also introduced what became known as "format effectors" or "control characters" – the CR (Carriage Return) and LF (Line Feed) codes. A few of Baudot's codes moved to the positions where they have stayed ever since: the NULL or BLANK and the DEL code. NULL/BLANK was used as an idle code for when no messages were being sent.

Baudot code Western Union

  • Keyboard of a teleprinter using the Baudot code, with FIGS and LTRS shift keys.

Baudot code Western Union

  • Murray's code was adopted by Western Union which used it until the 1950s, with a few changes that consisted of omitting some characters and adding more control codes. An explicit SPC (space) character was introduced, in place of the BLANK/NULL, and a new BEL code rang a bell or otherwise produced an audible signal at the receiver. Additionally, the WRU or "Who aRe yoU?" code was introduced, which caused a receiving machine to send an identification stream back to the sender.

Baudot code ITA2

  • Around 1930, the CCITT introduced the International Telegraph Alphabet No. 2 (ITA2) code as an international standard, which was based on the Western Union code with some minor changes. The US standardized on a version of ITA2 called the American Teletypewriter code (USTTY) which was the basis for 5-bit teletypewriter codes until the debut of 7-bit ASCII in 1963.

Baudot code ITA2

  • International telegraphy alphabet No. 2 (Baudot-Murray code)

Baudot code ITA2

  • Pattern of impulses

Baudot code ITA2

  • ITA2 is still used in TDDs, telex, and some amateur radio applications, such as radioteletype ("RTTY"). ITA2 is also used in Enhanced Broadcast Solution (a recent financial protocol specified by Deutsche Börse) to reduce the character encoding footprint

Baudot code Nomenclature

  • Nearly all 20th-century teleprinter equipment used Western Union's code, ITA2, or variants thereof. Radio amateurs casually call ITA2 and variants "Baudot" incorrectly, and even the American Radio Relay League's Amateur Radio Handbook does so, though in more recent editions the tables of codes correctly identifies it as ITA2.

Baudot code Details

  • NOTE: This table presumes the space called "1" by Baudot and Murray is rightmost, and least significant. The way the transmitted bits were packed into larger codes varied by manufacturer; the most common solution allocates the bits from the least significant bit towards the most significant bit (leaving the three most significant bits of a byte unused).

Baudot code Details

  • Table of USTTY codes (expressed as hexadecimal numbers)

Baudot code Details

  • In ITA2, characters are expressed using five bits

Baudot code Details

  • CR is carriage return, LF is line feed, BEL is the bell character which rang a small bell (often used to alert operators to an incoming message), SP is space, and NUL is the null character (blank tape).

Baudot code Details

  • Note: the binary conversions of the codepoints are often shown in reverse order, depending on (presumably) from which side one views the paper tape

Baudot code Details

  • The sequence RYRYRY..

Baudot code Details

  • US implementations of Baudot code may differ in the addition of a few characters, such as #, & on the FIGS layer. The above table represents the US TTY code.

Baudot code Details

  • The Russian version of Baudot code (MTK-2) used three shift modes; the Cyrillic letter mode was activated by the character (00000). Because of the larger number of characters in the Cyrillic alphabet, the characters !, &, £ were omitted and replaced by Cyrillics, and BEL has the same code as Cyrillic letter Ю.

Baudline

  • The 'baudline' Time-frequency representation|time-frequency browser is a signal analysis tool designed for scientific visualization. It runs on several Unix operating systems under the X11|X Window System. Baudline is useful for Real-time computing|real-time spectral monitoring, collected signals analysis, generating test signals, making distortion measurements, and playing back audio files.


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