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214 TELEPHONE USER PARTFigure 9.3-2. A successful international call.9.3.2 Successful International CallFigure 9.3-2 shows the setup of a successful international call. Exchanges V, W, andX are international switching centers (ISCs) in the originating country, a transitcountry, and the destination country. Exchanges V and W have seized internationaltrunks (T 1 ,T 2 ) with TUP signaling. In this example, address signaling is en-bloc,and no continuity checks are made.Exchange X seizes a national trunk T 3 with channel-associated signaling(CAS)—see Chapter 4. Exchange X is thus the last exchange in the TUP signalingsegment of the connection. We examine the information in the IAM and ACM.IAM Information. Exchange V has seized trunk T 1 to a transit country. The callednumber in its IAM (Section 9.2.1) is therefore an international number, and indicator(BA) is set to “international number.” Exchange W seizes trunk T 2 to the destinationcountry. It therefore removes the country code from the received called number,places the national called number in its IAM, and sets BA to “national number.” IndicatorH is set to “incoming international call” by the originating ISC (exchange V).Some international trunk groups are carried on satellite transmission systems. It isdesirable to have at most one satellite trunk in a connection (Section 1.4.6). If trunkT 1 is a satellite trunk, exchange V sets the IAM indicator DC to “satellite in connection,”and exchange W then selects a terrestrial outgoing trunk.Address Complete Message. Since trunk T 3 has CAS, the ACM is originatedby exchange X. It informs exchanges W and V that they can discard the callednumber and other setup data. In this example, ACM indicator F (Section 9.2.4) isset to “not a completely SS7 signaling path.”