Hi Rob,
A DUAMCO is a Duplexer Amplifier Multicoupler (In Siemens terminology). There are three versions 2:2,4:2 and 8:2. The first number is TRXs it can combine and the second number is output ports. Thus a 4:2 combiner can take output from 4 TRXs and combine them, so that they can be sent to two antenna ports ( 2 single polar ant or 1 cross polar ant ). The same ports receive the uplink signal from the antenna and split them into 8 parts ( after some isolation amplification etc.) to be distributed to 4 TRXs as main and diversity signals. Pl note that as the number of TRXs move from 2 to 8, the DUAMCO loss also increases.
Phew !! I hope that helps