| U.1 | Signalling conditions to be applied in the international telex service
		 
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| U.2 | Standardization of dials and dial pulse generators for the international telex service
		 
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| U.3 | Arrangements in switching equipment to minimize the effects of false calling signals
		 
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| U.4 | Exchange of information regarding signals destined to be used over international circuits concerned with switched teleprinter networks
		 
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| U.5 | Requirements to be met by regenerative repeaters in international connections
		 
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| U.6 | Prevention of fraudulent transit traffic in the fully automatic international telex service
		 
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| U.7 | Numbering schemes for automatic switching networks
		 
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| U.8 | Hypothetical reference connections for telex and gentex networks
		 
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| U.10 | Equipment of an international telex position
		 
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| U.11 | Telex and gentex signalling on intercontinental circuits used for intercontinental automatic transit traffic (type C signalling)
		 
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| U.12 | Terminal and transit control signalling system for telex and similar services on international circuits (type D signalling)
		 
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| U.15 | Interworking rules for international signalling systems according to Recommendations U.1, U.11 and U.12
		 
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| U.20 | Telex and gentex signalling on radio channels (synchronous 7-unit systems affording error correction by automatic repetition)
		 
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| U.21 | Operator recall on a telex call set up on a radiotelegraph circuit
		 
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| U.22 | 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 | 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 | Requirements for telex and gentex operation to be met by synchronous multiplex equipment described in Recommendation R.44
		 
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| U.25 | Requirements for telex and gentex operation to be met by code- and speed-dependent TDM systems conforming to Recommendation R.101
		 
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| U.30 | Signalling conditions for use in the international gentex network
		 
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| U.31 | Prevention of connection to faulty stations and/or station lines in the gentex service
		 
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| U.40 | 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 | Changed address interception and call redirection in the telex service
		 
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| U.43 | Follow-on calls
		 
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| U.44 | Multi-address calls in real time for broadcast purposes in the international telex service
		 
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| U.45 | Response to the not-ready condition of the telex terminal
		 
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| U.46 | Interruption of automatic transmission and flow control in the international telex service
		 
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| U.60 | General requirements to be met in interfacing the international telex network with maritime satellite systems
		 
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| U.61 | Detailed requirements to be met in interfacing the international telex network with maritime satellite systems
		 
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| U.62 | 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 | General requirements to be met in interfacing the international telex network with the maritime "direct printing" system
		 
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| U.70 | Telex service signals for telex to teletex interworking
		 
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| U.74 | Extraction of telex selection information from a calling telex answerback
		 
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| U.75 | Automatic called telex answerback check
		 
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| U.80 | International telex store and forward access from a telex subscriber
		 
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| U.81 | International telex store-and-forward - Delivery to a telex subscriber
		 
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| U.82 | 
[Withdrawn] International telex store and forward - Interconnection of telex store and forward units
		 
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| U.101 | Signalling systems for the Intex service (types E and F signalling)
		 
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| U.102 | Intex and similar services - Network requirements to effect interworking between terminals operating at different speeds
		 
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| U.140 | Definitions of essential technical terms relating to telegraph switching and signalling
		 
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| U.200 | The international telex service - General technical requirements for interworking
		 
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| U.201 | Interworking between the teletex service and the international telex service
		 
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| U.202 | Technical requirements to be met in providing the international telex service within an integrated services digital network
		 This Recommendation is also included but not published in I series under alias number I.560
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| U.203 | 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 | Interworking between the international telex service and the public interpersonal messaging service
		 
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| U.205 | 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 | Technical requirements for interworking between the international telex service and the videotex service
		 
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| U.207 | 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 | The international telex service - Interworking with the INMARSAT C system using one-stage selection
		 
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| U.210 | Intex service network requirements to effect interworking with the international telex service
		 
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| U.220 | The international telex service - Technical requirements for a status enquiry function in an interworking scenario
		 
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| U.Sup1 | 
[Withdrawn] Signalling characteristics and timing of the MARISAT telex service
		 
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| U.Sup2 | 
[Withdrawn] Signalling arrangements in the Maritime Satellite Telex Service via the MARISAT system
		 
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| U.Sup3 | 
[Withdrawn] Telex signalling arrangements in the Nordic Maritime Satellite coast Earth Station
		 
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