A downstream key, or DSK, is a graphic overlay on top of the regular video appearing on a television. It is added at the end of the feed before going to the Master Control switcher, and is usually relegated to the lower-third. This image is typically a bug, ghost, or crawl, but could be anything that fits the dimensions of the station's play to air format. Character generators, like a Chyron or Deko, can be used for downstream keying.