Brother PC-850D Operation Manual page 179

This message is displayed when the embroidery unit is attached
while the needle is lowered.
This message is displayed if the "START/STOP" button is
pressed while the foot controller is still connected.
This message is displayed if the "START/STOP" button is
touched when in editing mode.
This message is displayed if a non-buttonhole pattern is
selected and the "START/STOP" button or "REVERSE
STITCH" button is pressed while the buttonhole lever is
lowered.
This message is displayed if a buttonhole pattern is selected
and the "START/STOP" button or "REVERSE STITCH" button
is pressed while the buttonhole lever is raised.
This message is displayed when the embroidery pattern is
larger than the embroidery frame.
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