From Electro-Harmonix:

The Switchblade Pro is our deluxe switching box featuring true mechanical bypass, soft switching, high quality and low noise buffers, volume controls for all input signals, high headroom and a multitude of possible configurations for all your signal routing needs. This compact pedal is a versatile and indispensable tool!

• Switch between two amps or turn them both on at once
• Setup your effects loops to run in series or parallel, control what loops are on and, in series mode, what their order is.
• Multi-instrumentalists can connect up to three instruments into one amplifier
• Mix three instruments together and control the volume of each.
• With its Dry Level control, the Switchblade Pro is great for bass players
• The Switchblade Pro prevents tone-suck when vintage, non-true bypass pedals in its FX loops are disengaged.
• Can provide an adjustable volume boost with up to 6dB of clean gain
• EHX 9.6VDC-200mA power supply included