Synchronization. A term used in electronics to describe the precise alignment of two signals or functions. In video, sync is an essential element for maintaining the proper clocking of video signals. The sync signal is used by a monitor to know where and when to draw the on-screen video image. The horizontal sync signal is a short pulse generated at the beginning of each video line which tells the video monitor when to draw each new line. The vertical sync signal is a short pulse generated at the beginning of each video frame which tells the video monitor when to start a new field. Sync signals reside in the part of a video signal in which no visual picture information is transmitted. During this blanking period or horizontal or vertical interval, the electronic beam is blanked and retraces back to the other side of the screen to start a new line or new field. Since this is done during the blanking period, it is invisible to the viewer. Both horizontal and vertical sync are required in order to maintain a stable on-screen picture. Many video processing devices provide sync restoration and correction circuitry. Sometimes, a TBC is required to recover or restore sync.