The bandwidth for Basic Rate Interface ISDN would be used for residential connections, Primary Rate Interface ISDN with the higher bandwidth and expense was typically used inside of the telecommunication providers network and larger enterprises. Remember this was a time with 56Kbps dialup modems where the most prevalent connections at the time, so when ISDN provided two bearer channels (B Channels) at 64 Kbps, the customer would get a 128Kbps connection speed. If you where a larger organization you could get a combined speed of 1.54Mbps (with the 23 B channels that Ronnie mention earlier), with the ability to have more simultaneous parallel communications, as well as being the first converged communication technology (carrying voice, video and data over the same medium).
Best Regards,
Wes Bryan
Knowledge is a road to be traveled upon, not a destination to be reached~~