Overview of Electronic Speed Control
Electronic Speed Controllers (ESCs) are devices used on electronically powered radio controlled models to assist the motor speed, course and sometimes used in conjunction with braking systems.
They can be individual units that connect to the receiver's throttle control channel or integrated in the receiver, which is normal for most radio control vehicles. A number of radio control manufacturers that mount non-standard hobby-style circuitry in their low-end vehicles, boats or aircraft use onboard electronics that merge both onto one circuit board.
No matter what type is being used, an ESC deciphers control data not as mechanical motion like a servo, but instead in a way that varies the switching rate of a network of field effect transistors (FETs). The quick switching of the transistors causes the motor to give off its characteristic high-pitched noise, particularly noticeable at slower speeds. It also allows much smoother and more accurate variation of motor speed in a far more effective manner than the mechanical type with a resistive coil and moving arm once very common.