s, hardware> (CsU/DsU, or "..digital..") A device that performs both the channel service unit (CsU) and data service unit (DsU) functions. The Channel service Unit (CsU) is used to terminate a Ds1 or Ds0 (56/64 kb/s) digital circuit. It peformsline conditioning, protection, loop-back and timing functions. The Data service Unit (DsU) terminates the data circuit to the Data Terminal Equipment (DTE) and converts the customer' s data stream into a bi-polar format for transmission. (2001-10-19)