I suggest everyone read Hulda Clark 's book in order to find out these things. http://sbherbalremedies.com/books/the_cure_for_all_diseases.html Dr. Clark invented the zapper and I think she should know anything about zappers you need to know. I also suggest that you buy a hard copy because it helps her in her research. The online copy is a little bulky when copied so I will leave it to you to look it up.
It is not sensable to say that you have found a zapper (or anything else) that will do everything. If you agree with Dr Clark (which I do) you will have to agree with her methods (obviously) and regarding the zapper she said a 9 volt battery would work if you could tap twice a second for ten minutes. (pg 30) and "Any positively offset frequency kills all bacteria, viruses and parasites simaltaineously given sufficient voltage (5 to 10 volts), duration (seven minutes), and frequency (anything from 10 Hz to 500,000 Hz)." (page 15 top) This means the $10 zapper, and any other zapper as long as it is has a posative offset frequency, etc. (which they all, I assume do or they wouldn't be a real zapper) works just as well as any other. Lets focus on getting people well, not a war on weather 2500 (well between the Dr.'s 10- 500,000 Hz) works better than a 23kHz (also well between the Dr's reinge)
You should read pages 12-30 to understand fully what zapping is and why almost any type of zapper will work.
When you read her book you will notice she also says alot about avoiding mold toxins and solvants, using the right kind of soap etc. (all through the book after the zapper section) These are all very important and she has many specific remodies for diverse diseases. Anyway, you need to accually follow her recipes and cleanses carefully in order to rid yourself of the really serious diseases (I have never personally had a serous health problem, but I do trust Dr Clark as I have no reason not to and she has proved right so far)