Recommendation U.25
                        REQUIREMENTS FOR TELEX AND GENTEX OPERATION
                   TO BE MET BY CODE- AND SPEED-DEPENDENT TDM SYSTEMS
                           CONFORMING TO RECOMMENDATION R.101
                                            (Geneva, 1980)
                The CCITT,
          considering
                (a) that it may be desirable to use code- and speed-dependent  TDM  systems
          described in Recommendation R.101 in the teleprinter switching networks;
                (b) that it is essential to transmit the full range of  telex  signals  for
          types A, B, C and D signalling;
          unanimously declares
                that the following requirements for telex and gentex  operation  should  be
          met by code- and speed-dependent time division multiplex  systems  conforming  to
          Recommendation R.101.
          1      Transmission of type A (control) signals shall be accomplished within  the
          tolerances specified in Table 1/U.25.
          2      Transmission of type B (control) signals shall be accomplished within  the
          tolerances specified in Table 2/U.25.
          3      Transmission of type C signals shall be accomplished  in  accordance  with
          Table 3/U.25.
          4      Transmission of type D signals shall be accomplished  in  accordance  with
          Recommendation U.12.
          5      Each of the following modes of bothway telex signalling shall  be  capable
          of being accomplished on a single circuit:
                 a)  type A in one direction and type B keyboard in the other;
                 b)  type A in one direction and type B dial in the other;
                 c)  type B keyboard in one direction and type B dial in the other;
                 d)  type A in both directions;
                 e)  type B dial in both directions;
                 f)  type B keyboard in both directions;
                 g)  type C to Table 1/U.11;
                 h)  type C to Table 2/U.11;
                 i)  type C to Table 3/U.11.
          6      A single terminal shall be capable  of  handling  any  of  the  signalling
          combinations shown in S 5 above and at least five of them simultaneously.
          7      The nominal pulse duration  (other  than  dial  pulses)  shown  in  Tables
          1/U.25, 2/U.25 and 3/U.25 for Signal transmitted to telex have a ± 3 ms tolerance
          except where otherwise indicated.






























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                                                TABLE 1/U.25

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                                                TABLE 2/U.24

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                                                TABLE 3/U.25

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