Subscriber Trunk Dialling

Before STD (Subscriber Trunk Dialling) codes were introduced in Northern Ireland, during the 1960s and 1970s, an operator based system was in operation. Each subscriber had short (usually 3 or 4 digit) number within the local exchange. For example, the post office in Dromore was Dromore 201 .

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Subscriber Trunk Dialling - Exchange Code - England Phones

Subscriber Trunk Dialling England