A HDMI Switcher is an add-on component for your AV system that has several HDMI inputs and typically just one HDMI output. For example, a "4 In / 1 Out" switcher allows 4 source devices (such as DVD players, Sky Boxes, etc.) to be connected to it and the switcher into just 1 of your screen's HDMI inputs, therefore expanding the number of HDMI inputs by an additional 3. Switchers are available in a variety of configurations, including 2, 3, 4 and even 8 inputs, to further expand your TV's flexibility.