ANNEXE B: Connecting PHOENIX STRATOS to ISDN National-1.
The following paragraphs offer some practical notes for configuring the ISDN TERMINAL
ADAPTER (TA) in the UNITED STATES OF AMERICA and OTHER COUNTRIES using the
NATIONAL-1 ISDN PROTOCOL:
The ISDN (Integrated Services Digital Network) is a telephonic connection system that enables
its users to establish completely digital end-to-end communication. According to the number of
64-Kbps channels, there are two types of ISDN links: Basic Rate links (BRI) Primary Rate links
(PRI):
- The Basic links enable two data connections or channels to be established
simultaneously, each with a capacity of 64Kbps.
- The Primary links make it possible to establish 23 64-kbps channels in the United
States of America and 31 64-Kbps channels in Europe.
To access ISDN services, the would-be user must subscribe to an ISDN telephone line to which
a device can be connected, such as an audio encoder which is equipped with an ISDN Terminal
Adapter that will perform all the connection establishment and maintenance management
through ISDN digital telephone lines.
The PHOENIX STRATOS has an ISDN Terminal Adapter for Basic links (BRI), which gives it a
communication capacity of two independent 64-kbps data channels.
We can find two types of physical connections to the ISDN: connection to a U type interface and
connection to an S/T type interface:
- The U interface links the telephone exchange to the subscriber; it is a two-wire
interface of the type used in analog telecommunications, and permits only a point-to-
point connection (a single device connected to the interface).
- The S/T interface is obtained through the U interface by passing through a Network
Terminator (TR1) installed on the subscriber's premises; it is a four-wire interface that
permits the multipoint connection of up to seven devices.
In USA, telephone companies do not supply the TR1; it is up to users to install these devices if
they want them. The most usual situation is for the TR1 not to exist, and for the access to be
accomplished through the U interface.
In short, in USA the normal solution is access through the U interface unless the subscriber has
requested or the telephone company has installed a TR1 of its own volition. (The TR1 is
normally a little box secured to the wall with a power supply and a luminous indicator of some
type, into which the two-wire outside line enters, offering RJ-45 outputs).
The universal TA (Terminal Adapter) included in the PHOENIX permits both types of
connection. For that purpose, it is equipped with two ISDN connectors, one marked ETSI (RJ-
45, 8 pins) for connection through an S/T interface, and the other marked ANSI (RJ-11, 6 pins)
for connection through a U type interface. The type of connection used must be configured
during the equipment set-up procedure.
Although the ISDN is intended to be a uniform standard, differences can be found among the
protocols used in different countries. In USA, despite the presence of several protocols that are
incompatible with each other, there is, fortunately, one protocol that is relatively standardized
(called National-1), and which is usually available in all the telephone exchanges.
The Universal Terminal Adapter integrated into the PHOENIX STRATOS can operate with the
NATIONAL-1 protocol (the most frequently used protocol in the USA). The choice of the desired
protocol, in this case NATIONAL-1, must be configured during the equipment set-up.
In Europe and other geographic areas there is a protocol called EURO ISDN. There are minor
differences among the EURO ISDN standards applied in different countries. These differences
do not affect the PHOENIX STRATOS.
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