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1 Series and Recommendations

ITU-T issues recommendations that have names like X.500, where X is the series and 500 is a serial number.

See ITU-T recommendations.

Significant ITU-T series and recommendations are:

• A - Organization of the work of ITU-T
• B - Means of expression: definitions, symbols, classification,
• C - General telecommunication statistics
• D - General tariff principles
• E - Overall network operation, telephone service, service operation and human factors
  • E.123 Notation for national and international telephone numbers
  • E.163 Numbering plan for the international telephone service
  • E.164 The international public telecommunication numbering plan
    • Supplement 2 - Number Portability
• F - Non-telephone telecommunication services
• G - Transmission systems and media, digital systems and networks
  • G.711 Audio compression (mu-law)
  • G.722 Audio compression (wideband)
  • G.722.1 Audio compression (wideband, lower bit rates)
  • G.722.2 Speech compression AMR-WB (wideband, lower bit rates)
  • G.723.1 Speech compression CELP
  • G.726 Audio compression ADPCM
  • G.728728 is a ITU-T standard for speech coding operating at 16 kbit/s. Techology used is LD-CELP Low Delay Code Excited Linear Prediction. Delay of the codec is only 5 samples (1. The Linear prediction is calculated backwards with 50th order LPC filter. The ex Speech compression LD-CELP
  • G.729729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. Music or tones such as DTMF or Fax tones cannot be transported reliably with this codec, and thus use G. 711 or Out-of-band methods to transport Speech compression ACELP
• H - Audiovisual and multimedia systems
  • H.223 Multiplexing protocol for low bit rate multimedia communication
  • H.225.00 is a sub-standard of H. The main objective of H. 0 is the definition of messages: To establish, control and end an H. This set of messages is known as Call Signaling. The call signaling of H. 0 is based on Q. 931, the standard that defines the call sign Also known as RTPThe Real-time Transport Protocol (or RTP is developed by the Audio-Video Transport Working Group of the IETF and published in 1996 as. RTP was also published by the ITU-T as H. 0, but later removed once the IETF had a stable standards-track RFC published.
  • H.261261 is an increasingly obsolete 1990 ITU video coding standard specifically designed for transmission over ISDN lines in that data rates are multiples of 64 kbit/s. The standard supports CIF and QCIF video frames at resolutions of 352x288 and 176x144 resp Video compression standard, circa 1991
  • H.263263 is a video codec designed by the ITU-T as a low-bitrate encoding solution for videoconferencing. It was first designed to be utilized in H. 323 based systems, but now is finding use in RTSP ( streaming media) and SIP (Internet conferencing) solutions Video compression standard, circa 1995
  • H.263v2v2 is a video codec for low-bitrate video compression. Designed to supersede H. 263, it advances H. 263 by adding several annexes which substantially improve encoding efficiency. 263 page for more details. Video codecs ITU-T recommendations. (a.k.a. H.263+) Video compression standard, circa 1998
  • H.264 Video compression standard (also known as MPEG-4 part 10)
  • H.323 Packet-based multimedia communications systems
    • Annex D - Real-time facsimile over H.323 systems
    • Annex G - Text conversation and Text SET
    • Annex J - Security for H.323 Annex F
    • Annex K - HTTP based service control transport channel in H.323
    • Annex M.1 - Tunnelling of signalling protocol (Qsig) in H.323
    • Annex M.2 - Tunneling of signalling protocol (Isup) in H.323
  • H.324 Terminal for low bit-rate multimedia communication
  • H.332 H.323 extended for loosely coupled conferences
• I - Integrated services digital network ( ISDN)
• J - Transmission of television, sound programme and other multimedia signals
• K - Protection against interference
• L - Construction, installation and protection of cables and other elements of outside plant
• M - TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
• N - Maintenance: international sound programme and television transmission circuits
• O - Specifications of measuring equipment
• P - Telephone transmission quality, telephone installations, local line networks
• Q - Switching and signalling
• R - Telegraph transmission
• S - Telegraph services terminal equipment
• T - Terminals for telematic services
  • T.411 - T.424 Comprise the Open Document Architecture (ODA and ODIF), a standardized document file format
• U - Telegraph switching
• V - Data communication over the telephone network
  • V.1 Equivalence between binary notation symbols and the significant conditions of a two-condition code
  • V.21 A full duplex comminications protocol allowing two analog modems to signal each other at 300 bit/s, also operating at 300 baud.
  • V.22 A full duplex comminications protocol allowing two analog modems to signal each other at 1200 bit/s.
  • V.22bis A full duplex comminications protocol allowing two analog modems to signal each other at 2400 bit/s.
  • V.23 A half duplex comminications protocol allowing two analog modems to signal each other at 1200 bit/s.
  • V.24 List of definitions for interchange circuits between data terminal equipment ( DTE) and data circuit terminating equipment ( DCE) - equivalent to EIA RS 232, defined in ISO 2110.
  • V.25
  • V.26
  • V.26bis
  • V.27
  • V.27bis
  • V.27ter A full duplex comminications protocol allowing two analog modems to signal each other at 4800 bit/s
  • V.28
  • V.29 A comminications protocol allowing two fax to signal each other at 9600 bit/s
  • V.32 A family of 2-wire, duplex modems operating at data signalling rates of up to 9600 bit/s, full duplex for use on the general switched telephone network and on leased telephone-type circuits.
  • 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, with fallback to 12000 bits/s. This standard was improved on by modem manufacturers to create the V.terbo adhoc standard, signalling at 19,2 kb/s, as suggestive of a V.32ter standard that never materialized.
  • V.34 is the ITU-T standard for full-duplex data communications up to 28,000 bit/s with fallback to lower speeds depending on the remote modem ant the conditions of the phone line. This standard was known informally as V.Fast, hence pre-standard modems called V.FC (V.FastClass).
  • V.34+ (aka V.34bis) A communications protocol for full-duplex datacommunications up to 33,6 kb/s between two analog modems on dial-up lines.
  • V.42 Error correction protocol
  • V.42bis Data compression procedures for data circuit terminating equipment ( DCE) using error correction procedures to try to ensure the transfer of error-free data, even over the noisiest telephone lines. Ratified by CCITT in January 1990.
  • V.44 Data compression protocol
  • V.90 A digital modem and analogue modem pair for use on the Public Switched Telephone Network ( PSTN) at data signalling rates of up to 56 000 bit/s downstream and up to 33 600 bit/s upstream, using PCM encoding downstream, and QAM encoding upstream. V.90 Mode 2 used PCM upstream as well. This standard was known informally as V.Last and some pre-standard modems indicate V.Last compatibility or upgradeability. Prior to the arrival of the standard, there were two competing industry standards for 56 kb/s downstream signalling, X2 and K56flex. K56flex itself is a merged standard of K56 and 56flex.
  • V.92 A digital modem and analog modem pair for use on POTS at data signalling rates of up to 56 kbit/s downstream and up to 48 kbit/s upstream, using PCM encoding both ways, supporting Modem-on-Hold technology. This is a development of V.90 Mode 2.
• X - Data networks and open system communication
  • X.1 International user classes of service in, and categories of access to, public data networks and Integrated Services Digital Networks (ISDNs)

• • X.21 Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks
  • X.25 Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit
  • X.110 International routing principles and routing plan for public data networks
  • X.121 International numbering plan for public data networks
  • X.200 Information technology - Open Systems Interconnection - Basic Reference Model: The basic model
  • X.208 Specification of Abstract Syntax Notation One ( ASN.1)
  • X.209 Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1)
  • X.400 Message handling services: Message handling system and service overview
  • X.500 Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services Common text with ISO/IEC
  • X.509 Information technology - Open Systems Interconnection - The Directory: Public-key and attribute certificate frameworks
  • X.520 Information technology – Open Systems Interconnection – The Directory - Selected Attribute Types
  • X.521 Information technology – Open Systems Interconnection – The Directory - Selected Object Classes
• Y - Global information infrastructure and Internet protocol aspects
• Z - Languages and general software aspects for telecommunication systems

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