Hi, zappers are all about frequencies. From Tesla to Rife to Clark to many other researchers, applying the right frequency to the problem produces the desired result. If you have a Dr. Clark 7-20-7-20-7 basic zapper, your frequencies are right. This zapper is very good but the best thing to do is get a hand held frequency generator and get a list of frequencies that have been identified for a particular parasite. Here is a good site for starters:
http://www.bioelectric.ws/eng/freq-list.html
Write if you want more info, my time is limited but will try to help. PT