The shutoff arm is located over the ice bin and it rises up while the ice is being ejected and then drops back down afterward. If it does not drop down far enough, because the bin is full, no more ice will be made. Only after the ice level drops sufficiently, will the ice making cycle resume. The shutoff arm can be used to manually shut off the ice maker by moving it to the up position.
In component models, while the ejector motor is turning, a cam engages the holding switch and the water inlet switch. The holding switch temporarily keeps the ejection cycle going even though the shutoff arm has been raised up.
After the ice has been pushed out of the mold, the inlet switch signals the water inlet valve to release more water to refill the ice mold. The amount of water released is determined by how long the inlet switch remains depressed by the cam. Most ice makers have adjustments for controlling ice cube size. It may be a knob, lever or possibly a set screw hidden beneath the face plate. Increasing or decreasing the length of time the inlet switch is depressed will affect the amount of water that flows into the ice mold and thus the size of the ice cube.
On modular units the ejector motor momentarily completes a circuit to signal for water flow from the inlet valve.