A digital subscriber line access multiplexer (DSLAM, often pronounced dee-slam) is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques. Local loop: the telephone company wires from a customer to the telephone exchange or to a serving area interface, often called the  last mile  (LM). 2  Telephone exchange 3  : Main distribution frame (MDF): a wiring rack that connects outside subscriber lines with internal lines.