This revolutionary line output converter automatically detects the frequency range of your speaker leads, and a whole lot more! ^^ Attach the speaker wire to the KEYLOC, play a test tone and read the LEDs. ^^ Youll instantly know if Hi, Mid or Lo is coming from a particular pair of speaker wires. No oscilloscope or RTA needed! ^^ The KEYLOC allows you to keep or defeat factory time delay, or the all-pass filter built into many modern vehicles. ^^ By defeating this filter, the KEYLOC instantly counteracts the either of these factory effects, allowing you to tune for one-seat audio or maintain the factory imaging.