ITU-T V. telephone network standards

InternationalTelecommunicationUnion - Telecommunication Standardization Sector

The ITU (Click here for the ITU website) headquartered in Geneva, Switzerland is an international organization within which governments and the private sector coordinate global telecom networks and services. It was formerly known as the CCITT. The V Series Recommendations from the ITU-T are summarized below. Prior to the ITU-T standards, the American Telephone and Telegraph Company and the Bell System offered its own standards (Bell 103 and Bell 212A) at very low transfer rates. Another set of standards, the Microcom Networking Protocol, or MNP Class 1 through Class 10 (there is no Class 8), has gained some currency, but the development of an international set of standards means these will most likely prevail and continue to be extended. (Some Modems offer both MNP and ITU-T standards.)

In general, when modems "handshake," they agree on the highest standard transfer rate that both can achieve.

V.8 (2/98) Procedures for starting sessions of data transmission over the public switched telephone network.

V.8 bis (8/96) Procedures for the identification and selection of common modes of operation between data circuit-terminating equipment's (DCEs) and between data terminal equipment's (DTEs) over the general switched telephone network and on leased point-to-point telephone-type circuits.

V.17 (2/91) A 2-wire modem for facsimile applications with rates up to 14,400 bit/s.

V.18 (2/98) Operational and interworking requirements for DCEs operating in the text telephone mode.

V.19 (10/84) Modems for parallel data transmission using telephone signaling frequencies.

V.21 (10/84) 300 bits per second duplex modem standardized for use in the general switched telephone network.

V.22 (11/88) 1,200 bits per second duplex modem standardized for use in the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits.

V.22 bis (11/88) 2,400 bits per second duplex modem using the frequency division technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits.

V.23 (11/88) 600/1,200-baud modem standardized for use in the general switched telephone network.

V.24 (10/96) List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE).

V.25 (10/96) Automatic answering equipment and general procedures for automatic calling equipment on the general switched telephone network including procedures for disabling of echo control devices for both manually and automatically established calls.

V.25 bis (10/96) Synchronous and asynchronous automatic dialing procedures on switched networks.

V.26 (10/84) 2,400 bits per second modem standardized for use on 4-wire leased telephone-type circuits.

V.26 bis (10/84) 2,400/1,200 bits per second modem standardized for use in the general switched telephone network.

V.26 ter (11/88) 2,400 bits per second duplex modem using the echo cancellation technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits.

V.27 (10/84) 4800 bits per second modem with manual equalizer standardized for use on leased telephone-type circuits.

V.27 bis (10/84) 4,800/2,400 bits per second modem with automatic equalizer standardized for use on leased telephone-type circuits.

V.27 ter (10/84) 4,800/2,400 bits per second modem standardized for use in the general switched telephone network.

V.28 (3/93) Electrical characteristics for unbalanced double-current interchange circuits.

V.29 (11/88) 9,600 bits per second modem standardized for use on point-to-point 4-wire leased telephone-type circuits.

V.31 (12/72) Electrical characteristics for single-current interchange circuits controlled by contact closure.

V.31 bis (10/84) Electrical characteristics for single-current interchange circuits using optocouplers.

V.32 (3/93) A family of 2-wire, duplex modems operating at data signaling rates of up to 9,600 bit/s for use on the general switched telephone network and on leased telephone-type circuits.

V.32 bis (2/91) A duplex modem operating at data signaling 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.

V.33 (11/88) 14,400 bits per second modem standardized for use on point-to-point 4-wire leased telephone-type circuits.

V.34 (2/98) A modem operating at data signaling 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.

V.36 (11/88) Modems for synchronous data transmission using 60-108 kHz group band circuits.

V.37 (11/88) Synchronous data transmission at a data signaling rate higher than 72 kbit/s using 60-108 kHz group band circuits.

V.38 (10/96) A 48/56/64 kbit/s data circuit-terminating equipment standardized for use on digital point-to-point leased circuits.

V.41 (12/72) Code-independent error-control system.

V.42 (10/96) Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion.

V.42 bis (1/90) Data compression procedures for data circuit- terminating equipment (DCE) using error correction procedures.

V.43 (2/98) Data flow control.

V.50 (10/68) Standard limits for transmission quality of data transmission.

V.51 (11/88) Organization of the maintenance of international public switched telephone circuits used for data transmission.

V.53 (10/68) Limits for the maintenance of telephone-type circuits used for data transmission.

V.54 (11/88) Loop test devices for modems.

V.55 (11/88) Impulsive noise measuring equipment for telephone-type circuits.

V.56 (11/88) Comparative tests of modems for use over telephone-type circuits.

V.56 bis (8/95) Network transmission model for evaluating modem performance over 2-wire voice grade connections.

V.56 ter (8/96) Test procedure for evaluation of 2-wire 4 kHz voiceband duplex modems.
This Recommendation includes 2 diskettes containing the data files used for the throughput tests.

V.58 (9/94) Management information model for V-Series DCEs.

V.61 (8/96) A simultaneous voice plus data modem, operating at a voice plus data signaling rate of 4,800 bit/s, with optional automatic switching to data-only signaling 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.

V.70 (8/96) Procedures for the simultaneous transmission of data and digitally encoded voice signals over the GSTN, or over a 2-wire leased point-to-point telephone type circuits.

V.75 (8/96) DSVD terminal control procedures.

V.75 Append. II (2/98) Session establishment using V.75/H.245 procedures.

V.76 (8/96) Generic multiplexer using V.42 LAPM-based procedures.

V.80 (8/96) In-band DCE control and synchronous data modes for asynchronous DTE.

V.90 (9/98) A modem operating at data signaling rates of up to 56,000 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits. V.90 modems are designed for connections which are digital at one end and have only one digital-to-analogue conversion. Download speeds of up to 56,000 bits per second (bit/s) are possible, depending on telephone line conditions, with upload speeds of up to 33,600 bit/s. V.90 modems are designed for use on normal telephone lines where the connections are analogue at the customers premises and digital at the service providers premises. Unlike other modem standards, V.90 modems take advantage of the characteristics of the digital to analogue converters present in the telephone network to achieve hitherto unobtainable high rates of transmission.

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Last updated on May 06, 1999