Sync and Video : Working with Synchronization : Putting Pro Tools Online : Recording Online

Recording Online
The Operation Preferences page contains two options that affect how Pro Tools initiates recording when online.
Record Online at Timecode (or ADAT) Lock
Makes online recording begin as soon as Pro Tools receives and locks to timecode or ADAT sync. In this case, you do not need to make an insertion or selection in a track to designate a start point.
Record Online at Insertion/Selection
Makes online recording begin wherever you have placed the insertion point in a track. Recording then continues until Pro Tools stops receiving timecode. If you make a Timeline selection, Pro Tools will record online only for the length of the selection.