HDMI switches are used when multiple HDMI sources are distributed to multiple devices (Screens, projectors, AV amps etc). Generally used in pubs, clubs and offices. HDMI leads up to 20m can be utilised or Cat 5/6/7 for longer runs using the adaptor baluns. Infa red control of the HDMI source (Set top box, Bluray etc) can be fed via a seperate CAT5/6/7 cables.