Questions & Answers

What is 

STD full form 

ISD full form 

PCO full form

Where are these terms used?

Last updated date: 30th Jan 2023
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STD full form is Subscriber Trunk Dialling

ISD full form is International Subscriber Dialling

PCO full form is Public Call Office

The terms STD ISD PCO are used in the telephone system. They allow subscribers to dial trunk calls without operator assistance through trunk lines.