The PA-T3 serial port adapter is a single-width, one-port or two-port module that integrates data service unit (DSU) functionality into the Cisco router. It provides one or two high-speed serial PA-T3 interfaces on Cisco 7100 series routers, Cisco 7200 series routers, Cisco uBR7200 series routers, on the second- or fourth-generation Versatile Interface Processor (VIP2 or VIP4) in all Cisco 7000 series and Cisco 7500 series routers, and on the Catalyst RSM/VIP2 in the Catalyst 5000 series switches.