a) The diplexer is an additional thing to use before the connections go to the satellite receiver. You'd install a diplexer on one feed from the multiswitch and from the diplexer connect to the antenna input and one of the satellite intputs; another feed from the multiswitch would go directly to the other satellite input. b) If you run a separate line directly from the antenna, then no diplexer is used. This is how you do it whenever you need to get an antenna signal to some tuner input and the antenna signal is combined with a satellite signal. It doesn't matter what sort of receiver your using. The advantage comes about when you have more than one tuner that needs an antenna input or when you want to save on running a separate wire for the antenna signal. The power adapter is included with the multiswitch. If a multiswitch were passive (not powered) it wouldn't amplify the signal; each output of the multiswitch would be some percentage of the signal available since it's split 8 ways (on an Nx8 multiswitch). I've seen one 5x8 multiswitch that could operate without power (but also could be powered), every other one I've seen requires power.