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CSU/DSU – Channel Service Unit/Data Service Unit

Webopedia Staff
Last Updated May 24, 2021 7:39 am

Short for Channel Service Unit/Data Service Unit.

The CSU is a device that connects a terminal to a digital line. Typically, the two devices are packaged as a single unit. The DSU is a device that performs protective and diagnostic functions for a telecommunications line.

You can think of it as a very high-powered and expensive modem. Such a device is required for both ends of a T-1 or T-3 connection, and the units at both ends must be set to the same communications standard.