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)