Specifications

Overview of Dial Interfaces, Controllers, and Lines

ISDN Service

DC-11

Cisco IOS Dial Technologies Configuration Guide

The difference between traditional channelized lines (analog) and nonchannelized lines (ISDN) is that

channelized lines have no built-in D channel. That is, all 24 channels on a T1 line carry only data. The

signaling is in-band or associated to the data channels. Traditional channelized lines do not support

digitized data calls (for example, BRI with 2B + D). Channelized lines support a variety of in-band signal

types, such as ground start, loop start, wink start, immediate start, E&M, and R2.

Signaling for channelized lines is configured with the cas-group controller configuration command. The

following example configures E&M group B signaling on a T1 controller:

Router# configure terminal

Router(config)# controller t1 0

Router(config-controller)# cas-group 1 timeslots 1-24 type ?

e&m-fgb E & M Type II FGB

e&m-fgd E & M Type II FGD

e&m-immediate-start E & M Immediate Start

fxs-ground-start FXS Ground Start

fxs-loop-start FXS Loop Start

r1-modified R1 Modified

sas-ground-start SAS Ground Start

sas-loop-start SAS Loop Start

Router(config-controller)# cas-group 1 timeslots 1-24 type e&m-fgb

Router(config-controller)# framing esf

Router(config-controller)# clock source line primary

ISDN Service

Cisco routing devices support ISDN BRI and ISDN PRI. Both media types use B channels and

D channels. Figure 9 shows how many B channels and D channels are assigned to each media type.

Figure 9 Logical Relationship of B Channels and D Channels

BRI

2B + D

T1-PRI

23B + D

Used in North America

and Japan

E1-PRI

30B + D

Used in Europe

14051

B channel

D channel

B channel

D channel