The MA20 module extends the capabilities of the nVision Reference Recorder, allowing it to measure and log DC current, voltage and switch trip points. These modes are selected via the setup menu in the Crystal Control software which is provided with the nVision. Each nVision module is complete and independent, allowing the modules to be removed, exchanged, and even calibrated without the base. Please note that only one electrical or switch input can be monitored or recorded at a single time.