The purpose is to stop any operation to the end of limit when the reeler ends.
There are two rollers installed pressing the layers with spring loaded module.
When there is about one roller thickness of cable left in the reeler to be unwound, the bigger roller touches the drum radial surface and the rear arm of the roller assembly press the plunger of the limit switch.
This sends the signal to the PLC in the control panel top cut off power to the traversing motors.
Hence the traversing is stopped till the rollers have come off the radial surface of the drum.