The first time I used Basic frequency generator - 9 V. battery, 2 leads with alligator clips, 2 copper handholds. I started tapping one handhold, the other in my other hand. I felt as if my body shifted into a different state and had a moment of disorientation which passed within a minute. Other people I've talked to felt ill after the first zap. I have never had a die-off reaction or felt ill after zapping. After the Simple device I made and used a Zapper in a shoebox then have used a variety of commercial zappers. I'm using a Parazapper with 2 frequencies now. For viruses and Lyme I use it for longer times on both frequencies as the organisms are living in the cells and the zapper will only affect them when they burst out of the cells.