Cisco Systems, Inc. is the worldwide leader in networking for the Internet. Cisco products include routers, LAN and ATM switches, dial-up access servers and network management software. These products, integrated by the Cisco IOS software, link geographically dispersed LANs, WANs and IBM networks. Cisco offers a variety of expanding modules for Cisco routers to upgrade its abilities in order to meet growing demands of modern networking communications. The astonishing versatility of the Cisco router series is highlighted by its broad support of Integrated Services Digital Network Primary Rate Interface (ISDN PRI) connectivity.The available Cisco 3600 PRI network modules provide various port densities to meet customer requirements at various price points. The optional, integrated CSU lets customers consolidate customer premises equipment (CPE) to provide multifunction dial access server, router, and other capabilities within the Cisco 3600 series in power branch office environments. Cisco offers this two-port Channelized T1/ISDN PRI with Channel Service Unit (CSU) provides up to 24 virtual channels per T1 port.