ZX650.4 powering 2comps & 2 coax

Ok Thanks a lot! I have another question about this amp, it has two 4-pin connectors (+)(-)(-)(+) that say High level inputs, what are this for? the manual doesn't say anything except that if I use the HLI I should use the RCA dummy plugs in order for the fader to work properly. I don't even understand which fader means.

Maybe I shouldn't worry about that and just use the RCA's but I was just interested on learning what are those Inputs for. I will appreciate if someone can give me some info about it, Thanks again.