The modular architecture of the Cisco 2600 and 3600 Series allows interfaces to be upgraded to accommodate network expansion or changes in technology as new services and applications are deployed.Network modules enable the Cisco 2600 and 3600 Series to be customized to meet the needs of virtually any branch office. These modules support a broad range of applications, including multiservice voice/data integration, analog and ISDN dial access, serial device concentration or ATM access etc.