ATions, 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 peforms line 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)