A. The default is the E1 interface. To switch to T1, you need to remove the jumper cap inside the MTU board. Need to enter the Web management page to modify the configuration

B. None of the above

C. You only need to select E1 or T1 in the "Parameter Configuration> Transmission Mode" in the "Quick Configuration> Configure Board" page on the U1900 Web management page, and the switch can be completed

D. The default is T1 interface, switch to E1, you need to remove the jumper cap inside the MTU board, and you need to enter the Web management page to modify the configuration