Hello, Jade. There are many zappers to choose from, and a lot of people can get very confused about which one to pick. Here are a few important guidelines based on Hulda Clark 's books:
If a zapper plugs into a wall, don't buy it. If something goes wrong within that device, you are aligning yourself in a very strong, possibly lethal, current. Choose a zapper that is powered by a 9 volt DC battery, as Dr. Hulda Clark designed.
Dr. Clark wrote about avoiding wrist straps because they are not as conductive as copper handles. Make the most of the zapper current by using the most effective medium for conveying it to you. Only gold and silver is more conductive than copper. Wrist straps are also a safety hazard. I know, because I burned my wrist using the Syncrozap M1 in 2001. I didn't realize the wrist straps had dried up against my skin, and I didn't feel it burning. I still have a scar on my wrist to this day. Use a damp paper towel between your skin and the copper to protect you from the metal, and also to keep moisture.
Dr. Hulda Clark defines a Zapper as any unit that generates a positive offset frequency between 10 Hz and 500,000 Hz. In her early work she mapped out pathogen frequencies, but later found that it is the analog positive offset square wave quality that is most important in achieving results. Make sure the zapper you get does not have any spikes that go into the negative. Dr. Clark published schematics for 30 kHz (for basic zapping) and 1 kHz (for zappicating with a North Pole Speaker) only.
In earlier books, Dr. Clark recommended zapping 7 minutes 3 times with a 20 minute break in between. In later books, she wrote about the benefits of extending zapping to longer than 7 minutes as can be tolerated. Get a zapper that has a basic on/off switch, no automatic timer, so you can control how long you zap and not have to struggle with the timer switching you off after 7 minutes.