An electronic speed control or ESC is an electronic circuit that controls and regulates the speed of an electric motor. Smaller ESCs are used in drone applications and connect between the motor, power distribution board (PDB), and flight controller (FC). ESCs are generally either in a single or 4 in 1 configuration. Additionally, aside from the speed, they can also change the direction of the motor and provide what is called active braking of the motor. The programming controls all of this on the flight controller and the user's radio input.