Diplexers are signal COMBINERS, and work in pairs. Your incomming lines are labled SAT and ANT, and on the other side of the diplexer is IN/OUT. You can run your sat and cable feed into the correct labeled side of the diplexer into on cable...make sure your cable is atleast RG6 grade. Behind the receiver(s) you use the other diplexer to seperate (reverse the 2nd diplexer to seperate) the feeds to SAT and ANT (or in your case, cable tv). On the back of your receiver, you have an ANT/Cable input. Now...you can split the OUT TO TV lines to run your mirror images. If you have a cable box for Cable TV, just run the ANT side of the diplexer feed to the Cable box, and your OUT TO TV thru your Satellite receiver....then split your OUT TO TV from your satellite receiver to your mirrors. Than will allow you both SAT and CABLE on all 4 TV's. Ofcourse, if you wanted to watch cable tv, you'd need to shut off the satellite receiver to watch cable tv at both the receiver location and the mirror image on that line. Gosh, this is a pain to explain in text, isn't it? Ha! I hope I didn't confuse you....!