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1991-12-31
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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