What is the difference between the S/T interface and the U interface?
The U interface is found on the network side of an NT1 (network termination 1) and the S/T interface is found on the user side on the NT1. When you order an ISDN basic rate line in North America you are supplied with a two wire U interface and expected to source your own NT1 or connect a terminal which is fitted with an internal NT1. In Europe and some non European countries, the network operators install the NT1 as part of their service so you are expected to connect to the 4 wire S/T interface which is found on the user side of the NT1. In summary, North American customers will usually connect their terminals to the B-LinkU via the U interface and European customers will typically use the S/T interface.
