This is a tough question. In general, almost any frequency within the range of 10 Hz to 800 kHz can have some effect. It is just that certain exact frequencies may have more profound and noticeable effects. In that respect, the more accurate, the better. Sadly, there are few zappers that have better than even 1 percent accuracy.
>- Would you suggest I get other testing equipment ?
I would lean towards a decent frequency counter. I use a Leader LDC-822 for basic work.
>- What I do note is when a person is inserted with handholds in the circuit the zapper changes from square wave to sine wave on the scope.
This is a problem with the output of less powerful zappers. They are not able to output the amount of high frequency energy that is really needed. The best zappers will maintain a fairly good square wave even under load.
>- One other thing, have you ever tried or know someone that used the speaker (zappicator system)
I have tried several zappicators, and unlike zappers, they DO NOT work!
A simple test. take 2 ice cube trays ( not metal ) and fill them equally with stagnant water that is full of bacteria and protozoa ( infusoria ). Place one on a zappicator for an hour while the other is placed somewhere away and safe from any possible negative effects. Both should be kept at the same temperature, and environmental conditions. Using a microscope and compare the cultures. The sample that was on the zappicator will not show any difference than the controll that was not zappicated.
>- to project these frequency's into the body and more important directly to the tumor or what ever you want to treat. Acording to the manuals the RF frequency's preduced would go straight pass the wheelbearing greace and pcb's ect.