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.