CSU/DSU

a CSU/DSU connects LANs to WANs. CSU provides termination and diagnostics. DSU converts the electrical signal and provides data flow. a CSU/DSU terminates the line and converts electrical signals to be compatible with broadband networks.

what does a CSU/DSU stand for?
a stands for: Channel Service Unit / Data Service Unit

a CSU/DSU forms the connection point between a T1 line and the customer's internal network. CSU/DSU are two separate devices that are normally contained in one box. the t1 line terminates at the CSU, which monitors the connection for integrity and provides error correction. the DSU converts the signal used by internal bridges and routers into a signal that can be sent over th T1.