I did not know where to put this in health or gadgets as it belongs in both I love gadgets so when I seen this unit for pain and other uses. I wanted to build one because I could not afford the commercial units. After building one we experimented on many people all got relief some pain never returned. I made two different types one portable and the other uses house power. My unit is very basic but works just great. So for anyone who loves gadgets here you go. Here is two videos to give you some idea of PEMF. Here is the schematic and explanation. I used a 110 volt to 220 volt 50 watt [transformer] converter best if larger. Than used a diode bridge from there to a relay 40 amp. Which charged a bank of capacitors, or use a large photo flash capacitor. Other side of the relay is a coil of wire 120 -130 turns of #14 gauge wire. Word of caution when the capacitors are charged there are very dangerous when working with assembly make sure the capacitors are discharged. I fired the relay about every ten seconds if you want something faster you need to go to a larger transformer. Magnetic field travels about 6-7 inches in depth. Have fun Doug