Network Devices 45 It is used to terminate the end of a leased T-carrier line, which is a high-speed line that can be used to connect a LAN to a wide area network (WAN). It can be a separate component that attaches to a router and provides an interface. Newer routers have more modular capabilities that allow you to pur- chase what are sometimes referred to as WAN interface cards (WICs) that incorporate the CSU/DSU into the actual port and cable connection. Network Interface Cards NICs, also referred to simply as network cards, provide an interface to the network that allows data to be transmitted and received across the network media. Simply put, the NIC performs the following functions: It translates data from the parallel data bus to a serial bit stream for transmission across the network. It formats packets of data in accordance with protocol. It transmits and receives data based on the hardware address of the card. An NIC works as an interface between a computer's expansion bus and the