Duerkopp Adler 550-767 Operating Instructions Manual page 48

"EFKA" field
This function allows all of the functions of the EFKA d.c. motor to be
checked.
The settings made, e.g. initial lock-stitches, final lock-stitches, speed,
stitch length, etc., will be transmitted to the control unit by pressing the
"Transmit" key and one seam will be released.
HINT
Entries can only be made via an external operating panel of the type
V810 or V820.
"ELTEX" field
This function is for setting the thread tension in considering pre-set
tolerance limits, sewing speed, lifting height and stitch length.
See section 6.5: Needle-thread tension tolerance range.
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