Pulse/Function generators can either be internal circuits or pieces of electronic test equipments used to generate pulses. It usually allows control of the pulse repetition rate (frequency), pulse width, and the high- and low-voltage levels of the pulses. It may uses digital techniques, analog techniques, or a combination of both techniques to form the output pulses. For example, the pulse repetition rate and duration may be digitally controlled but the pulse amplitude and rise and fall times may be determined by analog circuitry in the output stage of the pulse generator. With correct adjustment, pulse generators can also produce a 50% duty cycle square wave.