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List of ITU-T V-series recommendations

(Redirected fromITU-T V.34)

TheITU-TV-Series RecommendationsonData communication over the telephone networkspecify the protocols that govern approvedmodemcommunication standards and interfaces.[1]

Note:thebisandtersuffixes are ITU-T standard designators of successive iterations of a standard (bisandterare derived from theLatinfor "twice" and "thrice" ).

General standards

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Applies to V.1–V.9

  • V.1is an ITU-T recommendation, entitledEquivalence between binary notation symbols and the significant conditions of a two-condition code.
  • V.2is an ITU-T recommendation, approved in November 1988, titledPower levels for data transmission over telephone lines.
  • V.4is an ITU-T recommendation, approved in November 1988, titledGeneral structure of signals of International Alphabet No. 5 code for character oriented data transmission over public telephone networks.
  • V.5was an ITU-T recommendation, approved in November 1988, titledStandardization of data signalling rates for synchronous data transmission in the general switched telephone network.It has been withdrawn since.
  • V.6was an ITU-T recommendation, approved in November 1988, titledStandardization of data signalling rates for synchronous data transmission on leased telephone-type circuits.It has been withdrawn since.
  • V.7is an ITU-T recommendation, approved in November 1988, titledDefinitions of terms concerning data communication over the telephone network.
  • V.8is an ITU-T recommendation, first approved in September 1994, titledProcedures for starting sessions of data transmission over the public switched telephone network.It has been superseded three times. The current version was approved in November 2000.
    • V.8bisis an ITU-T recommendation, first approved in August 1996, titledProcedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits.It has been superseded twice. The current version was approved in November 2000.

Interfaces and voiceband modems

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Applies to V.10–V.34

  • V.10is an ITU-T recommendation, first agreed in 1976, for unbalanced electrical circuits for data communication at up to 100kbit/s. It can interwork with V.28, provided it is not exposed to signals greater than 12 volts. Used with the 37-pin ISO 4902 connector, it is compatible with EIARS-423.
  • V.11is an ITU-T recommendation, first agreed in 1976, for balanced electrical circuits for data communication at up to 10Mbit/s. Used with the 37-pin ISO 4902 connector ( "DC-37"), it is compatible withEIA-422.The 15-pin ISO 4903 connector ( "DA-15") is recommended for data network interface.
  • V.17is an ITU-T recommendation for afaxmodem usingTCMmodulationat 12 and 14.4kbit/s.
  • V.18is an ITU-T recommendation for operation and interworking of text telephone devices
  • V.21is an ITU-T recommendation forfull-duplexcommunication between twoanaloguedial-upmodemsusingaudio frequency-shift keyingmodulationat 300baudto carrydigitaldataat 300bit/s.It is a variant of the originalBell 103modulation format.
  • V.22is an ITU-T recommendation forfull-duplexcommunication between twoanaloguedial-upmodemsusingPSKmodulationat 600baudto carry data at 1200 or 600bit/s.It is a variant of theBell 212Amodulation format.
    • V.22bisis an ITU-T recommendation extending V.22 with a faster rate usingQAMat 600baudto carrydigitaldataat 2400 or 1200bit/s.The 1200 bit/s mode is compatible with V.22.
  • V.23is an ITU-T recommendation forhalf-duplexcommunication between twoanaloguedial-upmodemsusingFSKmodulationat up to 600 or 1200baudto carrydigitaldataat up to 600 or 1200bit/srespectively. An optional 75 baud reverse channel carries 75bit/s.
  • V.24is referenced asRS-232which also includes V.28.
  • V.25terseeV.250
  • V.27teris an ITU-T recommendation for ahalf-duplexmodem,allowing 2400 and 4800 bit/s (PSKmodulation).
  • V.28is an ITU-T recommendation defining the electrical characteristics for unbalanced double-current interchange circuits.
  • V.29is an ITU-T recommendation for amodem,allowing 4.8 kbit/s, 7.2 kbit/s and 9.6 kbit/s transfer modes (PSKandQAMmodulations).
  • V.32 (11/88)is an ITU-T recommendation for amodemoperating asfull-duplexon a 4-wire circuit, orhalf-duplexon a two-wire circuit, allowing bidirectional data transfer at either 9.6 kbit/s or 4.8 kbit/s at asymbol rateof 2,400baudinstead of the 600baudof the V.22 standards.[2]
    • V.32bis (02/91)is an ITU-T recommendation for amodem,allowing up to 14.4 kbit/s bidirectional data transfer. Other additional defined data transfer rates are 12.0 kbit/s, 9.6 kbit/s, 7.2 kbit/s, and 4.8 kbit/s.[3]The standard was extended by several modem manufacturers to allow bidirectional data transfer rates of 19.2 kbit/s, but never ratified as a V.32terstandard. These non-ITU-T standard modems were often referred to as "V.32terbo"modems.[4]
  • V.33is an ITU-T recommendation for amodemoperating asfull-duplexon a 4-wire point-to-point leased line allowing bidirectional data transfer at either 14.4 kbit/s.
  • V.34 (09/94)is an ITU-T recommendation (superseded) for amodem,allowing up to 28.8 kbit/s bidirectional data transfer usingTCMmodulation.Other additional defined data transfer rates are 24.0 kbit/s and 19.2 kbit/s as well as all the permitted V.32 and V.32bis rates. Additionally, V.34 modems employ shell mapping asshaping codeto reduce the transmit power.[5]
    • V.34 (10/96)is an updated ITU-T recommendation for a modem, building on the V.34 standard but allowing up to 33.6 kbit/s bidirectional data transfer. Other additional defined data transfer rates are 31.2 kbit/s, as well as all the permitted V.34 rates. Modems implementing this standard were often marketed under the monikerV.34+.[6]
    • V.34 (02/98)commonly rendered as V.34bis, is a further update to V.34 which corrected some errata in the original 1996 document.[7]

Ad hoc standards

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In order to gainfirst-mover advantage,many modem companies introduced models based on upcoming V-series standards before they reached final ratification. In other cases, companies introduced non-standard systems but gave them ITU-like names.

  • V.32terbo,orV.32terfor short, was a 19.2 kbit/s standard introduced byAT&T Paradyne.It was based on V.32bis and did little other than increase the data rate. V.32ter is compatible with V.32bis at speeds of 14.4 kbit/s and lower, but it is not compatible with V.34 at 19.2.
  • V.FC,short forV.Fast Classand sometimes referred to asV.FAST,was developed byHayesandRockwellto introduce a 28.8 kbit/s standard while the V.34 efforts dragged on. V.FC was not compatible with V.34, although most V.34 modems could support V.FC, notably, those using Rockwell chipsets.[8]

Wideband modems

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Applies to V.35–V.39

  • V.35is an ITU-T standard located on layer 1 on theOSI model.Max speed is 2 Mbit/s and synchronous only. Withdrawn ITU-T recommendation for 48 kbit/s data transmission over wideband circuits. The physical and electrical characteristics of this interface are now specified in ITU-T recommendation V.11.
  • V.36is an ITU-T standard located on layer 2 on theOSI modelcalled Modems For Synchronous Data Transmission Using 60–108 kHz Group Band Circuits.

Error control and data compression

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Applies to V.40–V.49

  • V.41is a code-independent error control system. It defines theITU-TstandardCRC-16polynomial as x16+ x12+ x5+ 1
  • V.42is an error correction protocol. Its function is to allow the receiver to immediately request re-transmission of any lost data packets. However, it does not guarantee how quickly the error-free data will be delivered to the receiving end. V.42 is generally included in dialup modems. It also defines the ITU-T standard CRC-32 polynomial as x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1, and includes theLAPMframing protocol.
    • V.42bis,also an adaptive data compression standard, is based on theLempel Zivdynamic dictionary approach, and may go to "transparent mode," in which data is transmitted uncompressed. The specific algorithm is "BTLZ"(British Telecom Lempel Ziv), which was developed by Alan Clark (then with BT).
  • V.44is based onLZJH(Lempel-Ziv-Jeff-Heath) adaptive data compression developed by Hughes Electronics for its DirecPC satellite Internet, and incorporated into the v.92 dial-up modem standard. V.44 offers somewhat better compression performance for certain types of data than the V.42bis standard, on average allowing 15% greater throughput. For instance, a 53.3 kbit/s connection with V.44 can transmit up to 53.3×6 = 320 kbit/s using pure text. In reality, the overall data rate rarely exceeds 3:1 compression (~150 kbit/s). The compression tends to get better and worse over time due to noise on the line, or due to the transfer of already-compressed files (ZIP files, JPEG images, MP3 audio, MPEG video). At some points the modem will be sending compressed files at 53 kbit/s, uncompressed files at 160 kbit/s, and pure text at 320 kbit/s, or any value in between.[9][10]

Simultaneous transmission of data and other signals

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Applies to V.60–V.99

  • V.61Analog Simultaneous Voice and Data (ASVD)
  • V.70Digital Simultaneous Voice and Data (DSVD)
  • V.80:videoconferencing.It is generally compatibilized withH.324standard point-to-point video telephony over regular phone lines.
  • V.90is an ITU-T recommendation for amodem,allowing56 kbit/sdigital download and 33.6 kbit/s analog upload. It replaced two vendor standards (K56flexandX2) and was designed to allow modems from both prior standards to be flash upgraded to support it. It is also known asV.Lastas it was anticipated to be the last standard for modems operating near the channel capacity ofPOTSlines to be developed. V.90 is generally used in concert with the V.42bis compression standard.
  • V.91:A digital modem operating at data signalling rates of up to 64 000 bit/s for use on a 4-wire circuit switched connection and on leased point-to-point 4-wire digital circuits,published in 1999
  • V.92is anITU-Trecommendation, titledEnhancements to Recommendation V.90,that establishes amodemstandard allowing56 kbit/sdownload, 48 kbit/s upload rates, and the new V.44 compression method. It is intended to succeed the V.90 standards. With V.92,PCMis used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream data.

Interworking with other networks

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Applies to V.100–V.199

  • V.110is an ITU-T recommendation for using terminal adaptor functions for the connection of terminals having interfaces conforming to V-series to theISDN.
  • V.120is an alternative to V.110 based on the LAPD protocol.
  • V.150.1is an ITU-T recommendation for using amodemover IP networks.
  • V.152is an ITU-T recommendation for using Voice-Band Data over IP Networks.

Interface layer specifications for data communication

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Applies to V.200–V.249

  • V.230is an ITU-T recommendation, approved in November 1988, titledGeneral data communications interface layer 1 specification.

Control procedures

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Applies to V.250–V.299

  • V.250,originally known as V.25ter, is an ITU-T recommendation for serial asynchronous automatic dialing and control.[11]

Digital circuit modems

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Applies to V.300–V.399

  • V.300is an ITU-T recommendation, first approved in January 1997, titledA 128 (144) kbit/s data circuit-terminating equipment standardized for use on digital point-to-point leased circuits.

See also

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References

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  1. ^ITU-T(2006-09-29)."Data communication over the telephone network".ITU.Retrieved2008-03-02.
  2. ^"V.32: A family of 2-wire, duplex modems operating at data signalling rates of up to 9600 bit/s for use on the general switched telephone network and on leased telephone-type circuits".www.itu.int.Retrieved2020-08-20.
  3. ^"V.32bis: A duplex modem operating at data signalling rates of up to 14 400 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits".www.itu.int.Retrieved2020-08-20.
  4. ^Vendors rallying around high-speed modem scheme
  5. ^"V.34: a modem operating at data signalling rates of up to 28 800 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits".www.itu.int.Retrieved2020-07-05.
  6. ^"V.34: A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits".www.itu.int.Retrieved2020-07-05.
  7. ^"V.34: A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits".www.itu.int.Retrieved2020-07-05.
  8. ^"V.FC"
  9. ^Willdig, Karl; Patrik Chen (August 1994)."What You Need to Know about Modems".Archived fromthe originalon 2007-01-04.Retrieved2008-03-02.
  10. ^Mitronov, Pavel (2001-06-29)."Modem compression: V.44 against V.42bis".Pricenfees.com. Archived fromthe originalon 2017-02-02.Retrieved2008-03-02.
  11. ^Supplement (04/95) to Recommendation V.25ter - Serial asynchronous automatic dialling and control
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