Some professional monitors have an "in" and "out" BNC sockets for each R-G-B-S signal. If the "out" sockets are unused you need to put 75 ohm terminating plugs on each of the unused BNC inputs. This is for impedance balancing and stops un-wanted wave reflections. Some monitors have self-terminating (unlike the T-800 who was unable to self terminate) outputs in which case you will not need these terminating plugs. Please check your monitors user manual.