I be get picture pixillation and complete loss of some hd channel on one of my hdtv connect to my Comcast cable through a standard coax splitter that also serve another hdtv and my modem . replace that splitter with this unit and everything work perfectly -lrb- two hdtv and a modem -rrb- . a bi-directional unit be critical so that outbound traffic can be pass through -lrb- I have a old uni-directional power splitter that would not work -rrb- . only extra piece need be a coax cable to connect the splitter to the ac power supply that come with it .