The line6 FBV is a very versatile floorboard to control an amplifier (rack) for guitarists.
The downside of the FBV is only that it normally only works for Line6 Products. The FBV uses an own protocol and therefore cannot communicate direct with other equipment.
The FBV interface unit translates the FBV own protocol to MIDI. Also with additional configuration it is also possible to use the LEDs and display for feedback to the guitarist. (showing which units are on, what channel is selected, tuner output).
The devices it can communicate with are: