The 75-120-ohm adapter cable connects Cisco 120-ohm E1 port adapters to 75-ohm unbalanced G.703 E1 lines. The adapter has an eight-pin RJ-48C connector on the 120-ohm side and dual BNC coaxial connectors (transmit and receive) on the 75-ohm side. Two switches on the 120-ohm side allow the outer conductor of the cable (the input port of the E1 port adapter) to be either isolated from or connected to a protected earth ground. The 120-ohm E1 ports of your port adapter connect to the 75-120-ohm adapter cable using RJ-48C connectors and Category 3 or Category 5 shielded foil twisted-pair (FTP) cable with 120-ohm impedance.