Basic Rate Interface (BRI, 2B+D, 2B1D) is an Integrated Services Digital Network channel consisting of two 64 kbit/s "bearer" (B) channels and one 16 kbit/s "delta" (D) channel, giving a total data rate of 144 kbit/s. The B channels are used for voice or user data, and the D channel is used for control and signalling and/or X.25 packet networking. BRI is the kind of ISDN interface most likely to be found in residential service.
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