GENERAL KNOWLEDGE

Detailed explanation-1: -A technical standard and design philosophy for digital networks. ISDN provides high-speed, high-bandwidth channels to every subscribers on the public switched telephone network, achieving end-to-end digital functions with standard equipment interface devices.

Detailed explanation-2: -ISDN is a set of communication standards that uses digital transmission to make calls, transmit data and other network services over the circuit of the PSTN. ISDN delivers a combination of voice, video and data over a single line. Multiple devices can be attached to this line.