User`s manual

Am186™CC Microcontroller Router Reference Design User’s Manual

ISDN Background

Integrated services digital network (ISDN) is an alternative to analog phone lines.

ISDN provides greater performance than analog and is still affordable to

consumers. There are many different variations of ISDN available, but the most

common is 128-Kbit/s data transfer rate over two B (bearer) channels, plus 16-

Kbit/s of signaling data over the D channel; this is the 2B+D configuration, the

configuration used by the Am186CC microcontroller router reference design

discussed in this manual. Another configuration uses a single B channel and

transfers data at 64 Kbit/s. Broadband ISDN is available and can achieve data rates

in the 100-Mbit/s range.

There are a number of reference points in an ISDN system. Figure 0-2 shows a

graphical representation of the ISDN reference points. The U reference point is the

local loop between the Local Exchange (LE) and the Network Termination (NT)

device. The U interface is a two-wire interface, which in North America and Asia

is typically supplied by a telecommunications service provider. The U interface

operates in 2B1Q (two binary, one quaternary) format, and can travel for miles

without repeaters. The T reference point is used only with customer premises

switching equipment (NT2). The S/T reference point is the four-wire interface

between the network termination device (NT1) and the terminal equipment (TE1)

or Terminal Adapter (TA). The S/T interface is offered in Europe, and is also used

with stand-alone NT1 devices.

Figure 0-2. ISDN Reference Point Diagram

ISDN

Local

Exchange

(LE)

Te r m in a l

Adapter

(TA)

ISDN Terminal

Equipment

(TE1)

Non-ISDN

Ter minal

Equipment (TE2)

Network

Termination Type 1

(NT1)

Network

Ter mination Type 2

(NT2)

S/T

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