Also known as approximated or modified sine wave. Refers to a sine wave that instead of looking like a smooth curve where the voltage gradually ramps up and down over the course of the cycle, there are a series of “steps” or jumps in voltage from one plateau to another. Stepped sine waves are the result of the first stage of conversion of analog signals into digital, where instantaneous readings of the voltage are taken some number of times per second (the sample rate), but we mostly encounter them in electrical power. Stepped or modified sine waves are what are output from many UPS devices. In order to create an AC wave from a DC power source (which is essentially what a UPS is doing when activated) an electronic device known as an inverter is used. An inverter basically takes the DC voltage and uses it to trigger some type of oscillation, which results in a form of AC and is the type of output found in many commercial UPS devices. While not ideal in every situation modified sine waves (as opposed to true sine waves) are sufficient to operate many different types of equipment.