Inside the box is an geared motor powered by double A batteries and two switches: a toggle switch on the top of the box and a micro-switch inside. That's it.
The switches are positioned to be limit switches for the motorized arm. The toggle causes the motor to reverse, while a micro-switch powers down the circuit when the arm finishes retracting back into the box.
When idle, the circuitry is fully powered down. The toggle is “Reverse” direction, and the micro-switch is being held in the off position by the servo arm.
Keep in mind the micro-switch is wired up so that it works completely opposite from a normal switch like you would find in a doorbell. By using the common pin and the normally closed pin the micro switch is “OFF” when it’s button is being pushed.
When a person turns the toggle switch to the forward position, it also provides power to the motor causing it to rotate the arm towards the toggle switch.
As the arm moves away from it's off position it releases the micro-switch providing the backup power needed for the motor to retract after the toggle switch is turned off.
When the toggle gets switched “OFF” it actually reverses the motor’s direction. The arm reverses direction returning towards it's 'OFF' position. When the arm runs into the micro-switch it stops.
The toggle switch needed is a Dual Pole, Dual Throw (DPDT) toggle switch. This type of switch is actually a pair of switches which operate together (Dual Pole) and both are On-On (Dual Throw).