View source for CCIR 476

{{Short description|Character encoding used in radio data protocols}}
'''CCIR 476''' is a [[character encoding]] used in radio data protocols such as [[SITOR]], [[AMTOR]] and [[Navtex]].  It is a recasting of the [[ITA2]] character encoding, known as [[Baudot code]], from a five-bit code to a seven-bit code.  In each character, exactly four of the seven bits are mark bits, and the other three are space bits.  This allows for the detection of single-bit errors.

== Technical details ==
The number of possible valid binary code values in CCIR&nbsp;476 is the number of ways to choose 4&nbsp;marks for 7&nbsp;bit positions, and the number can be calculated using the [[binomial coefficient]]: <math>\ \textstyle \binom{7}{3} = \binom{7}{4} = 35\ .</math> Thus CCIR&nbsp;476 has 3&nbsp;additional [[code point]]s available over ITA2's 32 code points. 

The [[SITOR]] protocol uses the additional three code points (denoted as SIA, SIB and RPT below) for idle, phasing, and repeat requests.<ref>{{harvnb|Schetgen|1995|p=12.21}}</ref> In addition, some of the ordinary characters are reused as control signals.<ref>{{nobr|CCIR Rec. 625}} ''Service Information Signals''.</ref>

==Character set==
In these tables, the hexadecimal code values are converted from a binary representation, with 1 being mark, 0 being space, and the most significant bit given first.  The international version of ITA2 is used here; note also the added non-ITA2 codes SIA, SIB and RPT, used by SITOR.

{|{{chset-table-header1|CCIR 476 (Letter set)<ref name="arrl">{{cite web|url=http://www.discolodxgroup.cl/documentos/otros/ARRL%202013%20Handbook/ARRL%202013%20Handbook%20Supplemental%20Files/Chapter%2016/ITA2-CODES.pdf|title= ARRL 2013 Handbook, Chapter 16; ITA2 (Baudot) and AMTOR Codes|archive-url=https://web.archive.org/web/20220211215211/http://www.discolodxgroup.cl/documentos/otros/ARRL%202013%20Handbook/ARRL%202013%20Handbook%20Supplemental%20Files/Chapter%2016/ITA2-CODES.pdf|archive-date=2022-02-11|url-status=dead|date=2013}}</ref>}}
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|{{chset-ctrl1||[[SITOR#SITOR control characters|SIA]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+004A LATIN CAPITAL LETTER J|[[J]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0046 LATIN CAPITAL LETTER F|[[F]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0043 LATIN CAPITAL LETTER C|[[C]]}}
|{{chset-cell1|U+004B LATIN CAPITAL LETTER K|[[K]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0057 LATIN CAPITAL LETTER W|[[W]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0059 LATIN CAPITAL LETTER Y|[[Y]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0050 LATIN CAPITAL LETTER P|[[P]]}}
|{{chset-cell1|U+0051 LATIN CAPITAL LETTER Q|[[Q]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1||[[SITOR#SITOR control characters|SIB]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0047 LATIN CAPITAL LETTER G|[[G]]}}
|{{chset-ctrl1|U+000E SHIFT OUT|[[Shift out|FIGS]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+004D LATIN CAPITAL LETTER M|[[M]]}}
|{{chset-cell1|U+0058 LATIN CAPITAL LETTER X|[[X]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0056 LATIN CAPITAL LETTER V|[[V]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0041 LATIN CAPITAL LETTER A|[[A]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0053 LATIN CAPITAL LETTER S|[[S]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0049 LATIN CAPITAL LETTER I|[[I]]}}
|{{chset-cell1|U+0055 LATIN CAPITAL LETTER U|[[U]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
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|{{chset-cell1|U+0044 LATIN CAPITAL LETTER D|[[D]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0052 LATIN CAPITAL LETTER R|[[R]]}}
|{{chset-cell1|U+0045 LATIN CAPITAL LETTER E|[[E]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+004E LATIN CAPITAL LETTER N|[[N]]}}
|{{chset-ctrl1|U+000F SHIFT IN|[[Shift in|LTRS]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+0020 SPACE|&nbsp;[[Whitespace character|SP]]&nbsp;}}
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|{{chset-cell1|U+005A LATIN CAPITAL LETTER Z|[[Z]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+004C LATIN CAPITAL LETTER L|[[L]]}}
|{{chset-ctrl1||[[SITOR#SITOR control characters|RPT]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0048 LATIN CAPITAL LETTER H|[[H]]}}
|{{chset-ctrl1|U+0000 NULL|[[Null character|BLK]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+000A LINE FEED (LF)|[[Line feed|LF]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
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|{{chset-left1|7x}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+004F LATIN CAPITAL LETTER O|[[O]]}}
|{{chset-cell1|U+0042 LATIN CAPITAL LETTER B|[[B]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0054 LATIN CAPITAL LETTER T|[[T]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+000D CARRIAGE RETURN (CR)|[[Carriage return|CR]]}}
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{|{{chset-table-header1|CCIR 476 (Figure set)<ref name="arrl"/>}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1||[[SITOR#SITOR control characters|SIA]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+0007 BELL|[[Bell character|BEL]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0021 EXCLAMATION MARK|[[Exclamation mark|!]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+003A COLON|[[Colon (punctuation)|:]]}}
|{{chset-cell1|U+0028 LEFT PARENTHESIS|[[Bracket#Parentheses|(]]}}
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|{{chset-cell1|U+0032 DIGIT TWO|[[2]]}}
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|{{chset-cell1|U+0036 DIGIT SIX|[[6]]}}
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|{{chset-cell1|U+0030 DIGIT ZERO|[[0]]}}
|{{chset-cell1|U+0031 DIGIT ONE|[[1]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1||[[SITOR#SITOR control characters|SIB]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0026 AMPERSAND|[[Ampersand|&]]}}
|{{chset-ctrl1|U+000E SHIFT OUT|[[Shift out|FIGS]]}}
|{{chset-cell1|||style=background:#DDD}}
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|{{chset-cell1|U+002E FULL STOP|[[Full stop|.]]}}
|{{chset-cell1|U+002F SOLIDUS|[[Slash (punctuation)|/]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+003D EQUALS SIGN|[[Equals sign|=]]}}
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|{{chset-cell1|||style=background:#DDD}}
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|{{chset-cell1|U+002D HYPHEN-MINUS|[[Minus sign|-]]}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0027 APOSTROPHE|[[Apostrophe|']]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0038 DIGIT EIGHT|[[8]]}}
|{{chset-cell1|U+0037 DIGIT SEVEN|[[7]]}}
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|{{chset-left1|5x}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+0005 ENQUIRY|[[Enquiry character|ENQ]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0034 DIGIT FOUR|[[4]]}}
|{{chset-cell1|U+0033 DIGIT THREE|[[3]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+002C COMMA|[[Comma|,]]}}
|{{chset-ctrl1|U+000F SHIFT IN|[[Shift in|LTRS]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+0020 SPACE|&nbsp;[[Whitespace character|SP]]&nbsp;}}
|{{chset-cell1|||style=background:#DDD}}
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|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+002B PLUS SIGN|[[Plus sign|+]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0029 RIGHT PARENTHESIS|[[Bracket#Parentheses|)]]}}
|{{chset-ctrl1||[[SITOR#SITOR control characters|RPT]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+00A3 POUND SIGN|[[Pound sign|£]]}}
|{{chset-ctrl1|U+0000 NULL|[[Null character|BLK]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+000A LINE FEED (LF)|[[Line feed|LF]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|-
|{{chset-left1|7x}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0039 DIGIT NINE|[[9]]}}
|{{chset-cell1|U+003F QUESTION MARK|[[Question mark|?]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|U+0035 DIGIT FIVE|[[5]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-ctrl1|U+000D CARRIAGE RETURN (CR)|[[Carriage return|CR]]}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
|{{chset-cell1|||style=background:#DDD}}
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==References==
{{reflist}}
* {{Citation |editor-last=Schetgen |editor-first=Robert |title=The ARRL Handbook for Radio Amateurs |year=1995 |edition=Seventy-Third (1996) |publisher=The American Radio Relay League |location=Newington, CT |isbn=0-87259-173-5 |url-access=registration |url=https://archive.org/details/arrlhandbookforr00amer }}

[[Category:Character encoding]]
[[Category:Character sets]]
[[Category:Telegraphy]]
[[Category:Amateur radio]]