The Traveler, 4pre, Audio Express and UltraLite audio interfaces can operate via bus power (their Firewire connection to the computer). However, there may be times when you wish to power them from a wall outlet. This DC power supply allows you to do so. It has been extensively tested to confirm that it provides the correct power specifications, and the label even says "MOTU" on it, so you won't get it mixed up with power supplies for other products.