The Model 617S Video Chroma Keyer (Chromakey), Chroma Keyer, or Video Color Keying (Key) & Color Separation Overlay system, is a two-input, one-output, device that replaces a selected color in a "foreground" picture with details from corresponding areas of "background" picture. The video chroma key removes the selected color (chroma key blue screen or green screen, for example), or narrow range of colors, from the foreground image to "reveal" the background image "behind" it. This technique is also called video color keying, color key, blue screen chroma key, green screen chroma key, or color separation overlay. A switch allows selection of the foreground image only, or the keyed image consisting of elements from both foreground and background images. The Model 617S Video Chroma Key, Video Color Key & Color Separation Overlay system can also freeze the background input so that it can continue to be used for keying indefinitly.