Servo refers to an error sensing feedback control which is used to correct the performance of a system. Servo or RC Servo motors are DC motors equipped with a servo mechanism for precise control of angular position. They are used in robotic arms and legs, sensor scanners and in RC toys like RC helicopter, airplanes and cars.The servo motor can be moved to a desired angular position by sending PWM (pulse width modulated) signals on the control wire. The typical specifications of servo motors are torque, speed, weight, dimensions, motor type and bearing type.