PWM is a technical type of modulation. PWM is an abbreviation for the method of pulse width modulation, in which - at a fixed basic frequency - the on and off time of a square wave signal can be varied. The signal of a technical variable generated by PWM then alternates between two values. Frequency and duty cycle (ratio of switch-on and switch-off time of the square-wave signal, also called duty cycle) are variably adjustable with PWM. If the frequency is constant, the PWM modulates a square-wave pulse.