Disappointing to say the least - this is a unit for amateurs, it is not fully reliable or able to identify circuits. Too bad junk like this is on the market. My guess is that they tried to make a "consumer" model of a better unit, cheapened it up and got this. DON'T WASTE YOUR MONEY. Get a real tool, or just make a schematic of your house by turning off each breaker with a partner observing each recepticle or light.