What is CSU/DSU

CSU/DSU stands for Channel service unit and Data Service unit.  CSU/DSU is a pair of the communication devices that converts the LAN data frames into the size of WAN data frames.  CSU terminates the link at the customer’s premises.  It connects the terminal with the digital line. DSU performs the actual transmission and receives the signals.

It performs the diagnostic functions in the telecommunication networks. Normally, the CSU and DSU work together in the same unit.  CSU and DSU are two separate devices and one or both can be the part of the T1 WAN card.  The CSU and DSU are required for the communications on the digital lines.  A CSU/DSU has E1/T1 link on the media and FV1 on the equipment.