The Whirlwind Selector Multiselector Instrument Switch gives you the ultimate control over your instruments and your gear. You can alternate between channels A and B or select both. Send one guitar to two amps or use it the other way around to select between two guitars into one amp. Thanks to patented, state-of-the-art optical switching, there"s no added noise, pops or crackles and no alteration of your tone. Bright LEDs indicate channel status. Indestructible design means this pro quality box won"t let you down on the gig. Run it on one 9V battery or with optional external power supply (T401-ND).