API Audio 1608 Automation - Manual (Page 52)

The associated buttons on the faders will also illuminate to indicate the mode they are in.
MUTE WRITE cannot be assigned from the Status Page.
6.5.2 Fader Mode Assignment
Automation modes can be assigned to individual channels
by pressing the needed mode button on the fader module.
The mode button will illuminate to indicate that mode is
assigned and the corresponding channel in the Status Page
channel grid will change color.
MANUAL mode can be assigned on individual faders by
pressing and holding the READ button for at least 2
seconds.