CSU/DSU
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A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a router to a digital circuit such as a T1 or T3 line.
A CSU/DSU operates at the physical layer (layer 1) of the OSI model. CSU/DSUs are also made as separate physical products; CSUs and DSUs. Either or both may be part of a T1 WAN card inserted into a Data Terminal Equipment such as a router.
For digital lines, a channel service unit (CSU) and a data service unit (DSU) are required. The two are often combined into a single piece of equipment, called the CSU/DSU and both can be inserted as an interface card in a router slot. The CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. The DSU converts the T-carrier line frames into frames the LAN can interpret and vice versa. It also connects T-carrier lines with terminating equipment.
[edit] Application
A CSU/DSU has an E1/T1 link on the media side and may have FE1 and Ethernet ports on the equipment side. The media may be engineered over line/radio/OFC. The primary application of a CSU/DSU is to provide converged voice (CEPT) and data services over a standard T1/E1 links.
[edit] Line Speed
T1 is an American standard with 1544 kbit/s or 1.54 Mbit/s, while E1 is a European standard with 2048 kbit/s or 2.04 Mbit/s line speed.
[edit] WIC Wan Interface Card
The WIC (Wan Interface Card) contains an integrated CSU/DSU that can be fixed in to a Router slot ex . The 1-port 56/64-kbit/s DSU/CSU WIC (WIC-1DSU-56K4)check the following link from Cisco. [1]
