To the right is an illustrated schematic animation that contains a three phase pump motor starter with a hand off auto switch and two floats that control a sump pump.
MS1 is the pump motor starter.
The Hand Off Auto Switch is a three position switch with two sets of contacts. one set is made in hand and the other is made in auto.
The Red Lines show the circuit path.
The Switch is the heart of the circuit's path.
When the switch is in the off position there is no path to the coil and the pump starter can't run.
When in the hand position the path is directly connected to the coil and the starter is running the pump motor.
When in auto shown in the illustrated schematic animation the float switches control the pump starter.
When the bottom float is lifted by the liquid the circuit path is switched to the top float and one side of the MS1 contact (wire #2).
When the top float is lifted the path is complete to the coil. The contacts from MS1 close holding the path to the coil keeping the pump on until the bottom float is lowered or the switch is turned off interrupting the circuit's path.
Watch the circuit work to see what happens