CSU/DSU - Channel service unit / Data Service Unit

Try to Learn about this device, This is not commonly shown in CCNA Labs.

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The CSU/DSU provides signal timing for communication and is used for interfacing with the digital transmission facility.

•Essentially, the CSU/DSU is used by a router to connect to a digital line in much the same way that a PC uses a modem to connect to an analog line.

•A CSU/DSU for T1 will typically provide:

–Framing: ESF, D4(SF)

–Line Coding: AMI, B8ZS

–Multiplexing

–Cabling to Router: V.35, RS-232

–(more on these later) The CSU/DSU may also be built into the router. Like the card shown below.