How the Servo Motor Stabilizer work?

Hi guys,
Can anyone please explain how Servo Motor Stabilizer work? And if possible can anyone give me the circuit diagram?

Attached here picture for the device.

Hi,

You can read this article about servo stabilizers,
* http://www.stabilizer-regulator.com/voltage-stabilizer/servo-voltage-stabilizer-works
* http://www.electrical4u.com/servo-motor-servo-mechanism-theory-and-working-principle/

A servo voltage stabliser  will have a dimmerstat in its unit, the dimmerstat voltage seclection shaft is varied  by a motor whoes rotation is varied clock wise and anti clock wise depeding on the input voltage, if voltage is low the dimmerstat shaft moves clock wise to provide more voltage ie(230v ac )if less the reverse way to reduce the voltage, for clockwise and anti clock wise movment of the motor ,  two different circuits are provided in the unit. with a hi and low voltage sensing circuit also.