|  | 2.2 | WAN Devices
| 2.2.4 | CSU/DSUs on a WAN

A CSU/DSU is a digital-interface device-or sometimes two separate digital devices-that adapts the physical interface on a DTE device (such as a terminal) to the interface of a DCE device (such as a switch) in a switched-carrier network. The Figure illustrates the placement of the CSU/DSU in a WAN implementation. Sometimes, CSUs/DSUs are integrated in the router box.
| Threaded Case Study
Washington Project: Deployment of CSUs/DSUs

As part of the Washington School District network design and implementation, you need to determine what kind of CSU/DSUs to obtain, how many of them to obtain, and where to place them in the network. Possible locations include the MDFs in the school locations and at the main district office, where the WAN links will be terminated. Keep in mind that CSUs/DSUs need to be located close to routers.