When the stimulation waveform is generated by the DAC, it exists as a voltage-controlled signal. That is, the voltage is specified precisely as a function of time by the software (1 μs precision), but the stimulation current is allowed to vary freely (Figure 2B2). However, the signal can also be converted by the interface board to current-controlled stimulation, if the user wishes. With a current-controlled stimulus, the current is specified as a function of time, but the voltage delivered to the tissue is allowed to vary freely within a safe range, determined by adjustable voltage regulators and protection diodes (Figure 2B1). In either mode, both voltage and current can be simultaneously monitored for diagnostic purposes. Although current-controlled stimulation is more commonly used (Merrill et al., 2005), some studies, such as Wagenaar et al. (2004), have shown greater efficacy of voltage- over current-controlled pulses. Many commercially available stimulators are only voltage-controlled, or only current-controlled, but not both, and often produce only fixed biphasic or monophasic waveforms. Merrill et al. (2005) describe many cases where biphasic “square” pulses are more damaging than more complexly shaped stimulus waveforms. Thus, the flexibility of the NeuroRighter stimulator gives tangible benefits.