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[Datenschleuder] [36]    CCITT V.xxx standards
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CCITT V.xxx standards

Aus der internationalen Datenwüste

V.1 Defines binary 0/1 bits as space/mark line conditions
V.2 Limits power levels of modems used on phone lines
V.4 Sequence of bits within a character as transmitted
V.5 Standard synchronous signalling rates - dialup lines
V.6 Standard synchronous signalling rates - leased lines
V.7 Vocabulary
V.10 Unbalanced high-speed electrical interface characteristics
V.11 Balanced high-speed electrical characteristics
V.13 Simulated carrier control (full duplex modem used as half duplex)
V.14 Asynchronous to synchronous conversion
V.15 Acoustic couplers
V.16 Electrocardiogram transmission on phone lines
V.17 Application-specific modulation scheme for Group 3 fax(7.2,9.6,120,144) (provides 2-wire half-duplex trellis-coded transmission at 7200, 9600, 12000, and 14400bps.)
V.19 DTMF modems (low-speed parallel transmission)
V.20 Parallel data transmission modems
V.21 300 bps
V.22 1200/600 bps FDX
V.22bis 2400 bps
V.23 1200/75 bps (host tx 1200, rx 75, terminal tx 75, rx 1200) (Actually, V.23 can have only one channel or the other or both, and the channels are INDEPENDENT (not necessarily inreverse directions). The setup you've noted is typical of Prestel and other applications, but only one of many supported. V.23 also supports 600bps in the highspeed channel-I
V.24 known as EIA RS-232 in the USA [V.24 defines ONLY the functions of the circuits. EIA 232-E (which is how the current version of the standard is designated) also defines electrical characteristics and connectors. The 232-equivalent electrical characteristics are defined in CCITT V.28, and the equivalent connectors are defined in ISO2110.)
V.25 Automatic answering equipment and parallel automatic dialing (defines the 210011z "answer tone" that modems send)
V.25bis Serial automatic calling and answering - CCITT equiv of AT cmds) (this is the current CCITT standard for modem control by computers via serial interface (in the USA, we use primarily the Hayes AT command set)]
V.26 2400 bps 4-wire V.26bis 2400/1200 bps HDX V.26ter .2400/1200 bps FDX V-27 4800 bps 4-wire
V.27bis 4800/2400 bps 4-wire
V.27ter 4800/2400 bps FDX [V.27ter is also used in a half-duplex 2 wire mode to implement the 2400 and 4800 bps transmission shemes in Group 3 fax] V.29 9600 bps 4-wire [V.29 is also used in a half-duplex 2-wire mode to implement the 7200 and 9600 bps transmission schemes in Group 3 fax]
V.31 (Rarely used) older electrical characteristics based on contact closure (like old teletypes)
V.31bis The above, using optocouplers
V.32 9600/4800 bps FDX
V.32bis Ext'n of V.32; adds 7.2,120, and 144kbps ops & rapid rate renegotiation
V.33 14.4 kbps [and 12000bps, for 4 wire leased lines]
V.35 48 kbps 4-wire [The CCITT no longer recommends the use of V.35, since it was made obsolete by V.36. However, many computers and other equipment still use the electrical interface specified in Appendix 2 of V.35, and an particular ISO connector - and call it a "V.35" interface (although this is a misnomer)]
V.36 48 kbps 4-wire
V.37 72 kbps 4-wire [V.36 and, V.37 are not really "4-wire" modems. They are GROUP BAND modems, which means they combine several telephone channels (not just one)!]
V.40 How teletypes indicate parity errors
V.41 An older, obsolete error control scheme
V.42 Error-correcting procedures for modems using async-to-sync conversion (V.22, V.22bis, V.26ter, V.32, V.32bis); defines EAPM protocol, and provides fallback to MNP4
V.42bis Lempel-Ziv-based compression scheme for use with V.42 LAPM
V.50 Standard limits for transmission quality for modems
V.51 Maintenance of international data circuits
V.52 Apparatus for measuring distortion and error rate for data transmission
V.53 Impairment limits for data circuits
V.54 Loop test devices for modems
V.55 Impulse noise measuring equipment
V.56 Comparative testing of modems
V.57 Comprehensive test set for highspeed data transmission
V.100 Interconnection between PDNs and PSTNs (Public Data Networks, Public Switched Telephone Networks).
V.110 ISDN terminal adaption
V.120 ISDN terminal adaption with statistical multiplexing
V.230 General data communications interface, layer 1

The CCITT Blue Book, Volume VIII, Article VIII.1 contains the CCITT series V recommendations on "data communication over the telephone network".
'The list is not complete, but contains most of the stuff. You can order this article of the Blue Book for some $ at

Union Internationale des Telecomunications
Place des Nations
1211 Geneve 20

Toby Nixon, Hayes


  [Chaos CD]
[Datenschleuder] [36]    CCITT V.xxx standards
[Gescannte Version] [ -- ] [ ++ ] [Suchen]