is it MMU and SMU for Mini-Link?
if it is, MMU is the Modem Unit, where you connect your IF cable going to the RAU- radio unit that will be connected to the antenna. you will extract or map the E1s from the MMU going out to your cross connect terminal or DDF. SMU-switch multiplexing unit is used if you are going to do a Hot/Standby 1+1 mode.. 2 MMUs..