USB MIDI interface 4 in / 4 out, 64 channels for MIDI Keyboard, Expander, Groove BoxFeatures:3 in 1 Function, combined with USB MIDI, Merge and thru functions. 4 Inputs, 4 Outputs MIDI interface (64 MIDI Channels)MIDI Merge Function for mixing data of the inputs1 and 2, 4 outputPerfect MIDI timing, USB powered (no external power supply requires)High-speed connection to USB equipped PCTrue Plug and Play & Wide compatible, users do not need to install drivers.Mode SW: USB and MIDI THRU mode switch button. This button lets you choose one of the 5 operating modes of the interface ( One USB mode and 4 MIDI Thru modes)With this MIDI Box, you can obtain perfect midi timing and performance.MIDI in and MIDI out activity indicators for each port USB powered (no external power supply requires)Packing List:1X MIDI box1X Cable1X ManualNoticePlease keep in mind that THRU Mode only works when your computer is turned on as it need to be powered via USB port.