ISDN PRI (Europe)

The European telecommunications standard comparable to T-1 services is called E-1, and it
provides for 31 channels. (Time slot 0 is used for signaling and is not a channel in the ISDN
framework.) The last channel (actually channel 16) is used as a D channel for signaling, yielding
a total of 30 user bearer channels. As a significant aside, in Europe, the vendor typically provides
the network termination, whereas in the U.S., the customer usually provides it.
It is important to understand the differences between the North American
and European specifications. With either PRI or BRI, a U.S.-manufactured
ISDN router will not function elsewhere in the world because the NT is builtin.
As the service provider expects to provide the NT, the interfaces are
incompatible. ISDN routers manufactured elsewhere will work in the U.S. if
you add an external NT.
Consult with the vendor to determine the proper termination for E-1 PRI installations. These
should differ little from American installations, but there might be small alterations, which
could include, for example, providing the demarcation point on a wiring block. ISDN remains
popular in Europe and is likely to continue as an access technology there for some time, but
there is increasing evidence of DSL proliferation.
Chapter 26 addresses some of the differences in European ISDN specifications—
as compared to North American installations—in greater detail.
However, it’s important to note that the middle channel of the E-1 circuit (16)
is the D channel, contrasted with 24 in the T-1 specification. In addition,
T-1 starts numbering at 0, and E-1 starts with 1. (As noted before, channel
0 is used for framing.)