Rockwell Automation 2755-L7, -L9 Scanners - Manual (Page 25)

Chapter 4
Installation
4–3
The raster scanning models may occasionally experience raster rollover.
This condition is caused by jarring the scanner, excessive vibration, and will
occasionally occur upon power up.
The stepping of the raster motor is controlled by an incremental shaft
encoder, which has the ability to reset itself if one of the above conditions is
met.
Note: If the scanner is jarred during operation, labels may not be
scanned while the raster is resetting. In high speed operations, some
objects may not be scanned.
Vibration Cautions