A Pulse Width Modulation (PWM) Signal is used to control all kinds of electronic devices. A PWM signal is a short pulse of voltage which is typically repeated over and over in a very short amount of time, known as the period. Servos require a PWM signal, sent from a servo controller, to operate. The PWM signal sent to a servo is commonly quantified in microseconds (μsec). This range may vary from one servo to the next but most hobby servos will function properly on a PWM range of 1000-2000μsec. In hobby servos, the constants are generally the period (50Hz) and the pulse amplitude (3-5V). A change in PWM signal will cause the servo to rotate.