The egg tray must tilt every 4 hours. When the incubator controller is switched on it must determine the current position of the tray. If either motor switch sensors are activated it implies the tray is in the middle. As such it will activate the motor to the default position (LEFT) until the LEFT switch is activated and start the timer. If a switch is already active it will leave it in that position and start the timer. The following state diagram illustrates this logic.