Unlike DC stimulators, the “charge-balanced” biphasic waveform used by Checkpoint Nerve Stimulators does not allow the build-up of potential harmful charge during stimulation. By contrast, direct current stimulators deliver charge for as long as the stimulator is in contact with tissue.
Checkpoint's biphasic waveform elicits a highly visible “tetanic” (fused) muscle contraction. This is in contrast to DC stimulators, which elicit a single “twitch” response, making confirmation more difficult.