Recommendation U.4
                                 EXCHANGE OF INFORMATION REGARDING SIGNALS 
                              DESTINED TO BE USED OVER INTERNATIONAL CIRCUITS 
                                CONCERNED WITH SWITCHED TELEPRINTER NETWORKS
                           (former CCIT Recommendation E.4, Geneva, 1956;
                           modified at New Delhi, 1960 and Geneva, 1972)
               The CCITT,
         considering
               (a) that certain signals and certain characteristics of signals used in the
         international telex service have been standardized in Recommendation U.1;
               (b) that certain Administrations have introduced  automatic  telex  transit
         switching facilities based upon the signalling standards shown in  Recommendation
         U.1;
               (c) that standardized signals for the European  switched  network  for  the
         public telegram service (gentex network) are advocated in Recommendation U.30;
               (d) that in view of the foregoing an exchange of information regarding  the
         precise nature of the signals proposed to be used in the above-mentioned services
         by interested Administrations would be very useful;
               (e)  that  certain  Administrations  have  already  supplied  such  details
         regarding their telex services in a useful form (see supplements to the documents
         of the VIIIth Plenary Assembly of the CCIT, and subsequent Plenary Assemblies  of
         the CCITT),
         unanimously recommends
               that Administrations concerned  in  the  international  telex  service  and
         gentex network be invited to supply to the CCITT time-sequence  diagrams  showing
         in each case the signals at present transmitted or  proposed  to  be  transmitted
         over the international circuit for incoming calls. The diagrams should  show  not
         only the sequence and  characteristics  of  the  signals,  but  also  the  timing
         tolerances to be expected. The diagrams should  show  the  signalling  conditions
         applicable to transit as well as to terminal calls, including any  conversion  of
         the signals that are received from the destination network.






































                                                         Fascicle VII.2 - Rec. U.4   PAGE1