c
This enables key snapshot mode. In key snapshot mode, it is possible to save and recall key snapshots.
dKey source name display/key snapshot buttons
These show the signal name of the key fill selected for key 3 and the transition rate on two buttons. In key snapshot mode, these correspond to registers 1 and 2 for key 3; press to save or recall a key snapshot.
Panel Control and Menus 2 Chapter
204 Names and Functions of Parts of the Control Panel