The 2CE1 port adapters provide up to two channelized E1 (unbalanced 75-ohm or balanced 120-ohm) or ISDN PRI interfaces for connecting Cisco 7000 series routers to channel service units (CSUs). Each 2CE1 interface can transmit and receive data bi-directional at the E1 rate of 2.048 megabits-per-second (Mbps).Each 2CE1 interface connects to external networks through a single port that has a 15-pin, D-shell receptacle. You must use G.703 serial interface cables to connect unbalanced 75-ohm or balanced 120-ohm 2CE1 interfaces to a CSU. 2CE1 interfaces are configurable for balanced and unbalanced connections by setting jumpers on the 2CE1 printed circuit board.