CSU/DSU

this is what a CSU/DSU. when i used to work with the WAN team, they always mentioned CSU/DSU at the Demarc of the T1 i was troubleshooting, but i never knew how it looked, sometimes the carrier will have a CSU/DSU at their equipment when they hand of the circuit to us so we would never see it. finally this is how it looks like.

a CSU/DSU used for to connect LANs TO WANS. for example, you can have a private line or a dedicated T1 or T3 from the United States to India through a long haul carrier like AT&T. A CSU/DSU is like a NIC card that translates the signals with compatible broadband networks like TCP/IP