ISDN

As ISDN digital line has to channels and voice and data travel at same time, how does it occur? while considering DSL line where single data flow transmitted.
Anyone will explain to me please?

As ISDN digital line has to channels and voice and data travel at same time, how does it occur??

For ISDN, one line (B Channel(s)) is used for data and the other (D Channel) is used for signalling. Both data and voice run in the B channel(s).

The following might help you underatand the basics of ISDN:

www.firewall.cx/wan-tech-isdn-intro.php

For DSL, not the expert here.

ISDN provides a raw data rate of 144 Kbps on a single telephone company (called telco in the business) twisted pair. To better suit voice applications, this 144 Kbps channel is partitioned into subchannels: two 64 Kbps B (for bearer) channels and one 16 Kbps D (for data) channel. Each B channel can carry a separate telephone call and usually has its own telephone number, called a Directory Number (DN). You can combine the two B channels together to form a single 128 Kbps data channel through a process called bonding