Synchronizing with another video signal serving as a master timing source. The master timing source can be a composite video signal, a video signal with no active video (only sync information), or, for video studio, a device called house sync. When there is no master sync available, VideoFramer, for example, can be set to "free run" (or "stand-alone") mode, so that it becomes the master timing device to which other devices sync. See also line lock.