1976 also saw the introduction of International Subscriber Dialling ( ISD ) enabling local subscribers to dial direct to over 250 million telephones in 26 countries.
2.
During the introduction of International Direct Dialling ( IDD ), initially referred to as International Subscriber Dialling ( ISD ) within the UK, Group Switching Centres were equipped with international call timers and international register-translators to route calls to the relevant international exchange for onward routing abroad.
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