ITU-T U-Series Recommendations
(last updated: 19-Sep-1997 09:07)
U Series: Telegraph Switching
Telegraph Switching - General
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U.1 (03/93)
Signalling conditions to be applied in the international telex service.
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U.2 (12/56)
Standardization of dials and dial pulse generators for the international
telex service.
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U.3 (12/56)
Arrangements in switching equipment to minimize the effects of false
calling signals.
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U.4 (12/72)
Exchange of information regarding signals destined to be used over
international circuits concerned with switched teleprinter networks.
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U.5 (10/76)
Requirements to be met by regenerative repeaters in international
connections.
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U.6 (06/64)
Prevention of fraudulent transit traffic in the fully automatic
international telex service.
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U.7 (03/93)
Numbering schemes for automatic switching networks.
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U.8 (10/84)
Hypothetical reference connections for telex and gentex networks.
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U.10 (03/93)
Equipment of an international telex position.
Specific Signalling Schemes and Interworking Between Signalling Systems
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U.11 (03/93)
Telex and gentex signalling on intercontinental circuits used for
intercontinental automatic transit traffic (type C signalling).
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U.12 (03/93)
Terminal and transit control signalling system for telex and similar
services on international circuits (type D signalling).
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U.15 (03/93)
Interworking rules for international signalling systems according to
Recommendations U.1, U.11 and U.12.
Signalling Over Radio and Multiplexed Channels
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U.20 (12/72)
Telex and gentex signalling on radio channels (synchronous 7-unit
systems affording error correction by automatic repetition).
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U.21 (06/64)
Operator recall on a telex call set up on a radiotelegraph circuit.
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U.22 (06/64)
Signals indicating delay in transmission on calls set up by means of
synchronous systems with automatic error correction by repetition.
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U.23 (12/72)
Use of radiotelegraph circuits with ARQ equipment for fully automatic
telex calls charged on the basis of elapsed time.
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U.24 (10/68)
Requirements for telex and gentex operation to be met by synchronous
multiplex equipment described in Recommendation R.44.
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U.25 (11/80)
Requirements for telex and gentex operation to be met by code- and
speed-dependent TDM systems conforming to Recommendation R.101.
Gentex Signalling
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U.30 (12/60)
Signalling conditions for use in the international gentex network.
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U.31 (12/56)
Prevention of connection to faulty stations and/or station lines in the
gentex service.
Particular Signalling Facilities
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U.40 (03/93)
Reactions by automatic terminals connected to the telex network in the
event of ineffective call attempts or signalling incidents.
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U.41 (11/88)
Changed address interception and call redirection in the telex service.
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U.43 (11/88)
Follow-on calls.
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U.44 (11/88)
Multi-address calls in real time for broadcast purposes in the
international telex service.
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U.45 (03/93)
Response to the not-ready condition of the telex terminal.
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U.46 (03/93)
Interruption of automatic transmission and flow control in the
international telex service.
Radiotelex Interworking
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U.60 (10/84)
General requirements to be met in interfacing the international telex
network with maritime satellite systems.
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U.61 (03/93)
Detailed requirements to be met in interfacing the international telex
network with maritime satellite systems.
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U.62 (03/93)
General requirements to be met in interfacing the international telex
network with the fully automated maritime VHF/UHF radio system.
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U.63 (10/84)
General requirements to be met in interfacing the international telex
network with the maritime "direct printing" system.
Interworking Between New Information Services and Telex
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U.70 (10/84)
Telex service signals for telex to teletex interworking.
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U.74 (11/88)
Extraction of telex selection information from a calling telex
answerback.
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U.75 (03/93)
Automatic called telex answerback check.
Telex Store and Forward
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U.80 (03/93)
International telex store and forward access from a telex subscriber.
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U.81 (10/96)
International telex store-and-forward - Delivery to telex.
Intex Service
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U.101 (03/93)
Signalling systems for the Intex service (types E and F signalling).
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U.102 (07/96)
Intex and similar services - Network requirements to effect
interworking between terminals operating at different speeds.
Definitions
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U.140 (11/88)
Definitions of essential technical terms relating to telegraph switching
and signalling.
The International Telex Service
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U.200 (03/93)
The international telex service - General technical requirements for
interworking.
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U.201 (03/93)
Interworking between the teletex service and the international telex
service.
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U.202 (03/93) (same as I.560)
Technical requirements to be met in providing the international telex
service within an integrated services digital network.
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U.203 (03/93)
Technical requirements to be met when providing real-time bothway
communications between terminals of the international telex service and
data terminal equipments on a PSPDN or via the PSTN.
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U.204 (03/93)
Interworking between the international telex service and the public
interpersonal messaging service.
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U.205 (03/93)
Store-and-retrieve facility for the delivery of messages from a terminal
of the international telex service to a data terminal equipment which
connects to a packet-switched public data network over the public
switched telephone network.
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U.206 (03/93)
Technical requirements for interworking between the international telex
service and the videotex service.
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U.207 (03/93)
Technical requirements to be met for the transfer of messages between
terminals of the international telex service and group 3 facsimile
terminals connected to the PSTN.
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U.208 (10/96)
The international telex service - Interworking with the INMARSAT C
system using one-stage selection.
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U.210 (03/93)
Intex service Network requirements to effect interworking with the
international telex service.
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U.220 (03/93)
The international telex service - Technical requirements for a status
enquiry function in an interworking scenario.