Revo RU8NVR2AX User Manual page 69

Motion detection OR alarm triggered (M or A for short): recording

or snapshot is triggered when a motion detection alarm OR an input
alarm occurs.
When you choose an Event type of recording or snapshot, make sure you
have enabled the corresponding alarm function and configured alarm-
triggered recording/snapshot. The configuration steps are similar. See
Motion Detection Recording and Snapshot for more details.
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