Find Tracker、Transmitter. Usage: 1. Adjust your device Right-Top angle close 0° as you can. 2. Keep this angle then move your device along with narrow direction. 3. It will find out the Maximum MAGNETIC force source to your device. 4. Left-Top number is the volume of magnetic force e to your device. 5. If Left-Top number is greater than 150uT where shall be something.