Jam Sync is a mode available on many time code readers/generators/synchronizers. When jam synching, a TC reader/generator looks at external, incoming time code. It then “jams” or creates new time code based on that signal, identical to the original. There are two reasons for doing this: First, to replace degraded or defective time code. Second, when copying a time code track from one tape to another (mainly for analog tape, where each copy generation degrades the code signal).