This instructable describes how to drive hobby servos (the kind used in RC planes, cars, etc.) into your microcontroller projects. The control signals of servo are: a red wire, 5 volts works fine, ground (black wire) connectionsa and a control signal on the third wire (usually white or yellow). The signal is almost pulse width modulated, except that it doesn’t have a fixed period. It is composed of pulses of voltage, the duration of which determine the angle of the output shaft. The pulses can be from 0.9 ms to 2.1 ms long, 1.5 ms being the center position (in other words, pulse duration varies linearly with shaft angle).
Use a PIC Microcontroller to Control a Hobby Servo - [Link]