EuroISDN is now the standard in most parts of the world, except North America and certain other countries.

The EuroISDN network is supplied to the user through a box mounted on the wall. This box is called a Network Termination Type 1 or NT1.

The NT1 is part of the network and is the point at which the network service is supplied.

In North America (and some other countries) ISDN is supplied as a passive socket terminating the circuit to the ISDN service provider.