Dürkopp Adler 550-867 Operating Instruction page 57

Operation
Operating Instructions 550-867 - 00.0 - 11/2016
The remaining thread monitor (1) monitors the hook thread quantity
left on the bobbin inside the hook. If the light beam from the light
barrier is reflected by the surface (2) on the bobbin core during
sewing, a message will be displayed on the control panel. This
message indicates that only a small quantity of hook thread is left
on the bobbin.
The user can complete the seam and change the bobbin ( p. 37).
Fig. 40: Remaining thread monitor during use (3)
Process as follows when the remaining thread monitor (1) signals
that the hook thread is coming to an end:
1. Tap OK to confirm the message on the control panel.
2. Release the pedal before pressing it forward again.
3. Complete the seam you have started.
 The amount of thread in the supply groove (3) of the bobbin
is usually sufficient.
4. Press the pedal to position -2 at the seam end ( p. 69).
 The thread is cut.
5. Use Back to exit sewing mode on the control panel.
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