Cisco's Multichannel T1 cards offer high density, cost effective, and flexible connection to T1 links. More cost effective than serial interfaces with external CSU/DSUs, the Multichannel T1 cards have up to eight ports with built in T1 CSU/DSUs, and flexible configuration that allows any port to be configured for T1, fractional T1, channelized T1 and ISDN PRI services. Integrated T1 management and bit error rate testing simplify WAN administration. For sites that require T1 CSU and DSU functionality, the two-, four-, and eight-port Multichannel T1 port adapters provide the right mix of integration and cost. For service provider applications where only DSU functionality is required (for example, at sites co-located with a carrier), the eight-port Multichannel DSX1 card provides high port density at a reduced cost per port.