Hello. I lived in a state where I was able to find someone who had one that I could try. I am one of the rare individuals who could not physically tolerate it as it worked on me. It was very hard to take for even 10 minutes and that is about all the time I lasted. The person who let me try one, did not venture to guess why I was having a problem. Someone else referred to this 50 pages back but there was no real solution so I had to give up having the unit of my choice. I wound up getting the mini-FG which is not near as advanced at least not then. If you search page by page and look at the posts you will find quite a few references to the F-scan. It does not use the same set of frequencies as the Clark zapper does so if you are using her books for the tables in the back, there is a problem there but the posts explain how to convert and anyone you bought it from should know how to convert the frequencies. The mini-Fg is run by 9 volt batteries. The F-scan may not be. Don't quote me. It might even be plugged into the wall. The new mini-FG has a dither on it as some call it but they call it a wobble, something I wish my old mini- had and was looking for something at that time that had it but it wasn't made yet. It is possible the F-scan has that function but that is unknown to me. It is supposed to be extremely helpful for thorough parasite eradication. (the wobble effect) I see there must be different models but I think mine was the 165. Hope this helps at least a little.