The design is quiet, reliable and made to handle a lifetime of use. A/B two amps, pedal boards, or anything you can imagine. You can also flip it and use the input as an output and the outputs as two inputs. The A/B/Y has a dual color (red/green) LED for A&B and a yellow LED for the Y or both switch.Some examples: choose between two amps on the fly or between two guitars with no unplugging; take your tuner out of your signal chain or mute your guitar instantly. Anywhere you need to choose inputs or outputs, this box does the job!