Pro Tools LE locks to incoming MIDI Time Code (MTC). This is the way most affordable digital audio applications and hardware lock to time code. This takes care of the positional (location) reference part of locking up (meaning "where do you trigger the start of playback?"). As with most affordable systems, Pro Tools LE systems do not "resolve" the audio system's clock to an external tape deck (video or audio). This means that over longer periods of time, things can run very slightly out of sync because the "speed" that one system is running at is not forced to run *exactly* with the other. However, in real world practice, many musicians, editors and engineers deal with this every day when they work with such systems. That is, they depend on "MTC trigger" to lock to their source of time code. When you work with a very stable source (like MDMs such as ADATs or pro video decks), you can remain locked for long periods of time (i.e., even a couple of minutes).Note: If you really need to lock up so that the system is totally resolved (so that Pro Tools will change its *playback speed* continuously to match the source deck), then you'll want to buy a third-party option that allows you to resolve via the S/PDIF port on your Digi 001 or AM III hardware. These sync boxes are pretty expensive, so for many on a budget, this isn't really an option.