I actually have one of these devices that I bought new in the mid-eighties from The Tweak Shop. I keep it in its original box with instructions. If you require instructions, I can fax them to you if you provide me your fax number. It is used to correctly plug in a component's AC power cord in its correct orientation with respect to absolute polarity. Basically, you first disconnect all interconnects from the component. Then, plug in the supplied mini-connector into the unit and attach the other end to the component's chassis via an alligator clip. Next, you power up the component and push the appropriate button on the Namiki to power it and take a chassis voltage reading. Then, the AC plug is reversed and a second button is pushed and...Presto! The Namiki tells you which connection orientation is correct. Although the device works very well, I have never noticed any sonic differences in either orientation. Also, one spade of a component's AC plug is larger and the plug usually has a 3rd safety prong, so a cheater plug is necessary to do the test. Finally, if the Namiki shows that the AC plug must be oriented backwards, than the cheater plug must be left in place - ugh! It kind of makes me sick to think that I would need to put a cheap cheater plug on my very expensive exotic AC cord - that may degrade the sound more than having the thing plugged in the wrong orientation in the first place - how appalling! Hope this helps.