The modules can be used in T1 or E1 networks, selectable by software configuration. The integrated channel service unit/data service unit (CSU/DSU) function allows customers to consolidate customer premises equipment (CPE). The modules support balanced and unbalanced E1 connectivity and conform to the G.703 and G.704 standards for unframed and framed E1 modes. The Channelized T1/E1 and ISDN PRI modules work with the digital modem module in the Cisco 2800, 2900, 3800, and 3900 Series Integrated Services Routers to provide V.90- and V.92-compliant digital dial access aggregation.