Convert a Futaba S148 Servo to Continuous Operation
One of the simplest bots you can make is made by converting a couple of servos to free running mode. You get a small motor, gearbox and speed controller all in one package.
First lets talk a bit about how a servo works.
Most servos are controlled by a series of pulses. The width of the high state pulse is what determines the actual position of the servo.
Source: Detail information can be found in the following page
Where to Buy Futaba Servo?