Basic Rate ISDN (BRI) is divided into two forms, BRI-S and BRI-U. One of the main differences in them is the distance over which they can operate. BRI-S operates over the relatively short distance of 0.9km (3,000ft) where as BRI-U can operate up to 5.5km (18,000ft)
Many digital PBXs offer ISDN S-bus interfaces as standard. When there is a requirement for the S-bus to be located much further from the PBX then can be accommodated, the arcareach Sigma can be used to turn the S interface into a U interface.
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In order to connect BRI-S equipment an NT-1 is then required to convert back from a BRI-U interface to a BRI-S interface.
The arcareach Sigma can be used to provide a voltage supply on the U interface for any NT-1 that is connected.