I have this thing for ten years.
This is part of intelligent gadgets to be found for an electric guitar.
The principle excitatory magnetic coil is used as a "micro" and another powered by the battery, and excites the string vibrates.
So this interview notes and saves endless sustain!
Placed on top of the guitar pickups, you can even get sound distortion!
In short, experiment!!
The most Ebow provides the excitement of fundamental chord, or its harmonics! And there, with scores lower strings are amazing!

A tool that takes time to master, but worth it!