It's suspose to be a magical fish attracting device. All the major stores ( Bass Pro, Cabelas, etc.) sell it or a version of it. It's powered by your 12 v dc battery. It attaches to the stern or a few other ways. It's function is to alter the electrical charges around your boat. Ther are several ways that you can hook it up. One way is to hook it up around your downrigger wire. It looks like a small loop (coil) that goes around the downrigger line. It has wires the hook up to the Black Box. You can dial in a certain amount of voltage for a selected species of fish. It's a very interesting concept. The book is interesting. Now I peaked your interest along with the other 18,000 that view this site.