Telecommunications Guide
Evolution of Telephony in India: How STD and ISD Codes Connect the Country
A look at subscriber trunk dialing, tier-1 city landline codes (011, 022, 033, 044, 080), and international ISD codes.
1. History of Subscriber Trunk Dialling (STD) in India
Before 1960, long-distance telephone calls in India required manual intervention by trunk telephone operators. On November 25, 1960, India's first direct Subscriber Trunk Dialling (STD) service was launched between Kanpur and Lucknow.
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