Duerkopp Adler 550-867 Service Instructions Manual page 91

"Sewing motor"
When this function is activated all the functions of the Efka DC motor
can be checked.
The preset settings like initial bartack, end bartack, speed, stitch
length and so forth will be transmitted to the control unit via pressing
the "Send" button and a seam will be seam will be triggered.
Note:
These entries can only be carried out via external operating panel of
the type V820.
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