Serial network interfaces reside on modular port adapters, which provide a direct connection between the high-speed bus in the router and the external networks. The one-port PA-T3 serial port adapter provides two network interfaces per VIP2 for the Cisco 7000 series and Cisco 7500 series routers, the Catalyst 6000 family FlexWAN module, and the Catalyst RSM/VIP2, and one high-speed interface on the Cisco 7200 series and Cisco uBR7200 series routers. The PA-T3 serial port adapter provides a full-duplex synchronous serial PA-T3 interface for transmitting and receiving data at rates of up to 34 Mbps.