The dial shelf controller (DSC) card is the main processor card for the dial shelf. It links the dial shelf to the router shelf, where data is transferred as Ethernet packets encapsulated in proprietary protocol and interconnects trunk cards and modem cards. A backplane interconnect concentrator on each dial shelf controller card connects to each dial shelf card installed in the dial shelf.The DSC card boots and reloads software images and provides source clocks used by all dial shelf cards and power supplies. It also extracts an external reference clock from an external E1 or T1 signal through a BNC connector on the front panel and connects to an external alarm source through a DB-15 serial connector located on the front panel. The card plugs directly into the backplane. It serves as the interface between the dial shelf and the Cisco 7206 router.