Versatile, 2-way signal routing tool Instantly switch between two inputs or two outputs, or to use two inputs or two outputs simultaneously. For example: alternate between two different amps or amp channels; or quickly switch between two guitars going into one amp. In A or B Mode, the footswitch is used to select either Input/Output A or Input/Output B. In Y (A+B) Mode, both Input/Output A and Input/Output B are in use simultaneously, and the footswitch is inactive.