DESC: The ADTRAN Quad Basic Rate ISDN (BRI) Module contains four ISDN S/T interfaces and combines with other ATLAS 550 components to implement an ISDN access switch. The Quad BRI Module can emulate the ISDN network to other ISDN access devices (NT mode) that support the S/T-interface, such as routers, video codecs, terminal adapters, and network termination units.