CSU/DSUS—Connecting Devices to a Digital Line
Channel service units (CSUs) are required to interface with digital T-1, T-3, fractional T-1 and T-3, switched 56-Kbps and dedicated 56-Kbps lines. T-1 allows 24 voice, data and video transmissions to share one telephone circuit. T-3 circuits carry 672 voice, data and video transmissions (see Chapter 6). They also are used with E-1 and E-3 European service. Often, CSUs are cards within multiplexers and PBXs rather than standalone, external devices.
Although they have different functions, CSU/DSUs are supplied in one integrated piece of equipment. At one time, the DSU and CSU were sold as separate “boxes.” Functionally, the CSU sits between the telephone line and data service unit (DSU). The CSU plugs ...
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