1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 “ TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-%!.3G0G0/(b) that the ISO is the international organization concerned with standardization in the field of data processing;(c) that IEC Technical Committee No. 25 has requested the CMV to assist with the def
2、inition of letter symbolsfor terms and units used in data communication,recommends(1) that the CCIs should use the terms “bit, “baud”, “shannon”, “byte” and “N-bit byte” with the definitionsestablished by the ISO and the ITU and appearing in Annex A;(2) that the term “bit” is synonymous with “binary
3、 digit” and is also used in the letter symbol for this unit; theterm being an abbreviation of the English term “binary digit” and being adopted also in French and Spanish; formultiples of this unit and for derived units the letter symbols kbit, Mbit, kbit/s should be used;(3) that the unit “baud” sh
4、ould have as its letter symbol Bd with possible multiples of kBd and MBd;(4) that the unit “shannon” should have as its letter symbol Sh;(5) that for the terms “byte” it is the task of the ISO to provide the letter symbol it judges to be necessary. Inthe meantime this term and its multiples should b
5、e written in full in the documents and texts of the CCIs. For example10 kilo- bytes, 1 mega-byte. The term “N-bit byte” has no multiples.ANNEX A(to Recommendation B.14)A.1 binary digit, bitF: lment binaire, bitS: digito binario, bitA member of a set of two elements commonly used to represent informa
6、tion.Note In the interest of clarity, it is recommended that the term “bit” shall not be used in two-condition start-stop modulation instead of “unit-element”.A.2 binary digit rate, bit rateF: dbit binaireS: velocidad binariaThe number of binary elements transferred in a time interval divided by tha
7、t time.Note: The binary digit rate is expressed in bits per second (bit/s) and multiples of this unit._1)A similar text will be submitted to the CCIR as a revision of Recommendation 607-1.2 Fascicle I.3 - Rec. B.14A.3 baud (symbol: Bd)F: baud (symbole: Bd)S: baudio (smbolo: Bd)The unit of modulation
8、 rate in telegraphy and data communication or the unit of line digit rate in digitaltransmission; when expressed in terms of this unit, the modulation rate or line digit rate equals the reciprocal of theduration in seconds of the shortest signal element or of the unit interval in a digital signal co
9、mposed of signal elementsof constant duration.Example If the duration of the unit interval is 20 milliseconds, the modulation rate is 50 bauds.A.4 shannonF: shannonS: shannonA unit of logarithmic measure of information equal to the decision content of a set of two mutually exclusiveevents expressed
10、as a logarithm to base two.Example: The decision content of a character set of eight characters equals 3 shannons (log28 = 3).A.5 byte octet, 8-bit byteF: octetS: octeto (byte)An ordered set of 8 binary digits operated upon as an entity.A.6 n-bit byteF: multiplet n-upletS: multibit n-bitAn ordered set of a specified number of binary digits operated upon as an entity.Note This definition is compatible with the definition of ISO (Data Processing Vocabulary, Part 4: DataOrganization).
