User`s manual

EAGLE - ANNEX A.3. EUROISDN communications guide (EUROPE) 60
A.3. EUROISDN communications guide (EUROPE)
1.- Notes about the ISDN and the peculiarities of the different types of ISDN
1.1.- Generalities about the ISDN
The ISDN (Integrated Services Digital Network) is a telephone connection system that permits
the establishment of fully digital end-to-end communications.
There are two types of ISDN links, depending on the number of 64 Kbps channels: Basic links
(BRI – Basic Rate Interface) and Primary links (PRI – Primary Rate Interface).
Basic links allow the simultaneous establishment of two connections or data channels, each
with a capacity of 64Kbps.
Primary links allow 31 – 64 Kbps channels to be established in Europe and 23 - 64 Kbps
channels in USA.
To access ISDN services, you must subscribe to an ISDN phone line and connect equipment to
it, such as an audio codec, that has an ISDN Terminal Adapter device to perform the tasks of
establishing and maintaining connections through digital ISDN phone lines.
The Eagle has an ISDN Terminal Adapter for Basic links (BRI), which gives it a communications
capacity of two independent 64 Kbps data channels. Eagle allows these channels to be grouped
into a single 128 Kbps channel, doubling the bandwidth and the communications cost.
1.2.- Types of connection to Basic ISDN Links
We can find two types of physical connection to the ISDN: connection to a type U interface, and
connection to a type S/T interface.
The U interface connects the telephone exchange with the subscriber. It has two wires; the
same as in conventional analog line (telephony), and only allows a point-to-point connection (a
single device connected to the interface).
The S/T interface is obtained from the U interface, passing it through a Network Terminator
(NT1) located at the subscriber’s premises. It has four wires and allows a multipoint connection
of up to 7 devices.
In Europe, phone companies put the NT1 directly on the subscriber’s premises, and force
access through the S/T interface.
In summary, access in Europe is always through the S/T interface. This is made up of two
transmit lines, one for each direction of the communication, and each of the lines must have a
load of 100 ohms at each end. At the NT1 end, the NT1 itself gives the load. At the other end,
the load may be located at some point on the bus cabling (usually on the connector furthest
from the NT1) or inside one of the pieces of equipment connected to it. The Eagle has two
internal jumpers that allow you to configure whether the termination will be made inside the
equipment or not. By default (factory configuration), these jumpers are set, with the termination
being made (100 ohms load) in both directions inside the equipment.
In the USA, phone companies do not supply the NT1, so the user is the one who must install it if
he wants it. The most common situation is for there to be no NT1, and therefore access is
through a U interface.
The Eagle’s universal TA (terminal adapter) allows both types of connections, and thus has two
ISDN connectors, one marked ETSI (RJ-45, 8 pins) for the S/T interface connection, and the
other marked ANSI (RJ-11, 6 pins) for the type U interface connection. The type of connection
used must be configured in the unit’s setup.