Lindsay

While Colin is certainly correct in saying that not all cards have built-in DSUs, I believe that it is not the best answer in this case. Cisco sometimes implements the same functions on different cards in different ways. A customer of mine uses many 1841s with serial cards. Many of these cards do have the built in DSU, but there is no separate controller interface. Instead the controller commands are entered as service-module commands under the serial interface such as these:

service-module t1 remote-loopback payload v54

service-module t1 timeslots 1-24

These were taken from an 1841 with the WIC-1DSU-T1-V2 card. So in this case Cisco has implemented the controller functionality commands under the serial interface rather than implementing a separate controller interface.

HTH

Rick