Using USB connectivity, the research-grade Vilistus digital sampling unit (DSU) includes four ports.  The encoder transmits the standard 256 data samples per second from the sensors in use to the Mind Mirror software. Up to four EEG sensors can be used at a time for group brainwave training or a combination of any four sensors. Compact, portable and easy to use, the Vilistus DSU is the most affordable, powerful, and accurate neurofeedback/biofeedback device on the market. Two-year warranty.