Mixing : Automation : Automation Modes : AutoJoin with Latch Mode

AutoJoin with Latch Mode
(Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
Pro Tools provides two different methods to resume writing automation on controls that were active at the point where the transport stopped:
AutoJoin
Lets you automatically resume writing automation in Latch mode.
Join
Lets you manually resume writing automation in Latch mode. Join is available only with supported control surfaces.
To enable AutoJoin from Pro Tools:
1 Choose Window > Automation.
2 Click the AutoJoin button.
 
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See your control surface guide for details on using Join and AutoJoin with a control surface.
AutoJoin Indicator
After a Latch automation pass with AutoJoin enabled, the AutoJoin indicator appears in the Pro Tools Edit window.
 
The AutoJoin indicator is a vertical line that signifies the point where the last automation pass was stopped, and the point where the “join” will automatically occur on all tracks that were writing during that previous pass. When automation writing is resumed from this point, the line disappears.
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To use Join or AutoJoin to resume writing on controls that were writing when the transport stopped, restart the transport before the AutoJoin indicator.