Recommendation U.6
                        PREVENTION OF FRAUDULENT TRANSIT TRAFFIC 
                  IN THE FULLY AUTOMATIC INTERNATIONAL TELEX SERVICE
                             (New Delhi, 1960; amended at Geneva, 1964)
               The CCITT,
         considering
               (a) that, with fully automatic working in the international telex  service,
         the possibility of fraudulent  routing  by  subscribers  of  international  calls
         involving tandem connection of international telex trunks  might  arise  whenever
         subscribers are given automatic access to international telex trunk circuits that
         have,  at  their  incoming  ends,  automatically   switched   access   to   other
         international telex trunk circuits;
               (b) that, by the adoption of a systematic plan, such traffic can be  barred
         without involving either expensive or elaborate equipment arrangements;
               (c) that, to be effective, such a plan would need  to  be  adopted  by  all
         Administrations and  recognized  private  operating  agencies  since  failure  to
         provide barring facilities on the traffic between two countries  could  open  the
         way for irregular routings at the expense of a third country,
         unanimously declares the view
               (1) that national telex systems shall be so arranged that the  first  digit
         of the selection signals transmitted over  incoming  international  telex  trunks
         will indicate whether an automatic transit call is concerned;
               Note - The use  of  a  common  first  digit  to  indicate  access  to  both
         international telex trunk circuits and manual switchboards leads to  complication
         in the barring arrangements and should therefore be avoided as far as possible.
               (2) that where  an  international  telex  trunk  carrying  fully  automatic
         traffic also carries traffic requiring access at  the  incoming  end  to  outlets
         selected by means of the digit characterizing  an  automatic  transit  call,  the
         country of origin will bar irregular routings by  discriminating  on  the  digits
         transmitted by calling subscribers;
               (3) that where  an  international  telex  trunk  carrying  fully  automatic
         traffic does not carry traffic requiring access at the incoming end by  means  of
         the digit characterizing an automatic transit call, the incoming equipment  shall
         be so arranged that the corresponding outlets are not accessible  and  that  when
         access is attempted the number unobtainable signal is returned;
               (4) that it is not admitted that two Administrations can agree to omit  the
         provision of barring facilities on traffic between  their  respective  countries.
         However, where the incoming country has an existing network in which considerable
         difficulty would be experienced in barring in accordance  with  S  3  above,  the
         responsibility for barring may, by agreement, be assumed by the country of origin
         in the manner specified in S 2.




























                                                         Fascicle VII.2 - Rec. U.6   PAGE1