ISDN stands for

AIntegrated Services Digital Network ✓ Correct

BIntelligent Services Digital Network

CIndividual Services Digital Network

DImage Services Digital Network

Correct answer: (A) Integrated Services Digital Network

Explanation

ISDN expands to Integrated Services Digital Network, carrying voice and data digitally over phone lines.

Intelligent Services Digital Network is not the correct expansion of ISDN.

Individual Services Digital Network misstates the first word, which is integrated.

Image Services Digital Network is likewise not what ISDN denotes.

The name reflects that many service types are integrated onto one digital network.

ISDN was an early step from analogue toward fully digital telephony.

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