NT1S—Connecting Devices to an ISDN Line
Devices such as video teleconference units, PCs, PBXs, key systems and multiplexers that are connected to ISDN lines need an NT1 interface to the ISDN line. As reviewed in Chapter 6, ISDN enables voice, data and video to share one telephone circuit. The network termination type 1 (NT1) corrects the voltage on the signals. It provides the electrical and physical terminations to the carrier's network. In addition, the NT1 provides a point from which line monitoring and maintenance functions can take place. On BRI ISDN services, NT1 devices change the ISDN circuit from two wires that come into the building from the central office to the four wires that are needed by ISDN equipment. (BRI ISDN circuits carry ...
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