It took me a bit to figure out how I was going to power this, then I remembered that I had a Shark power supply. These come with around a dozen different tips and I found one that fit. Power on button on top, a very simple device that does what it says. Accurate tuning. You plug your guitar in on the 'in' port, and the 'out' port can go to an amp. The light up display makes it easy to see, very clear with no blurry glow. Overall, a decent tuner.