DESC: The BayStack ISDN BRI option provides two 64 kilobit-per-second (Kbps) B channels for data and one 16 Kbps D channel for signaling. This feature is supported on the single Ethernet, single Token Ring, and Ethernet/Token Ring BayStack AN router, and the BayStack ANH router/hub models. If an ISDN BRI port configured with two B channels and one D channel is enabled, only one synchronous port (COM2) is active.