The DS4 takes an analogue voltage waveform defined within your own data acquisition/ control system and converts it into an isolated constant current stimulus. The DS4 will accept several input voltage ranges and produces four output ranges (±10µA, ±100µA, ±1mA and ±10mA). It also features a GATE input, so that several DS4 units can be controlled by a single analog waveform, but enabled individually via this GATE input. A timed "inactivity sensor" reduces battery usage and damaging "leak currents" during infrequent stimulation, while at the same time maintaining low levels of zero crossing distortion for repetitive waveforms.