Pulse generators are electrical test equipment used to generate pulses that are injected into devices under test in order to study the behavior of these devices. Basic pulse generators allow users to control the frequency or pulse repetition rate, the pulse width, pulse high-voltage and pulse low-voltage levels, and a delay for an internal or external trigger. More complex products allow control over the rise time and fall time of the pulses. To form outputs, pulse generators may use analog techniques, digital techniques, or both. For example, analog circuitry may be used to control parameters such as pulse amplitude, rise time, and fall time. Digital controls can be used to determine the pulse repetition rate and duration.