Welcome to ISDN / 55N0130943 02 Modular ICS 7.1 Installer GuideB channelsB channels are the bearer channel. They are used to carry voiceor data information and have speeds of 64 kbps. Since eachISDN line (BRI or PRI) has more than one B-channel, morethan one transmission can occur at the same time, using asingle ISDN line.D channelsThe standard signaling protocol is transmitted over a dedicateddata channel called the D-channel. The D-channel carries callsetup and feature activation information to the destination.This channel has speeds of 16 kbps (BRI) and 64 kbps (PRI).Data information consists of control and signal informationand packet-switched data such as credit card verification.ISDN layersISDN layers refer to the standards established to guide themanufacturers of ISDN equipment. The layers include bothphysical connections, such as wiring, and logical connections,which are programmed in computer software.When equipment is designed to the ISDN standard for one ofthe layers, it works with equipment for the layers above andbelow it.There are three layers at work in ISDN for Norstar. To supportISDN service, all three layers must be working properly.Tip - Norstar PRI supports the D-channel on the 24thchannel only. Norstar does not include support for abackup D-channel on the span.
