Alpha Synopsys offer subrack holds one MCU-x and up to 16 ULAF+ plug-in units. Cascading of up to 4 subracks is possible to manage up to 64 plug-in units with one controller card. Backplane access to the line cards’ E1 and Ethernet interfaces minimizes costly cabling where MCU’s Ethernet concentration or TDM over Ethernet functionality is needed. Management communication between line cards and the MCU is done over a high performance backplane bus.