Question

What do you mean by STD and ISD​

Answer 1

Explanation:

International Subscriber Dialling

International Subscriber DiallingISD (International Subscriber Dialling) stands for International calls, STD (Subscriber's Trunk Dialling) for Inter-state calls and PCO (Public Call Office) for local calls. The system still exists but those small yellow booths which used to be everywhere around a city are vanished completely.

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Answer 2

Answer:

ISD (International Subscriber Dialling)

STD (Subscriber's Trunk Dialling)