Cisco offers a wide variety of connectivity, expansion and upgrade options to accommodate the range of application needs in customer networks. The network modules assure customers that they can choose a connectivity solution that fits their requirements. They are easily and inexpensively upgradeable as customer requirements change.The channelized E1/ISDN PRI modules are available with one or two E1 ports with balanced or unbalanced interfaces and are compatible with the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) G.703/ G.704 specifications. The channelized E1/ISDN PRI modules receive and transmit data bidirectionally at the E1 rate of 2.048 Mbps and provide up to 30 virtual channels per E1 port.