The frequencies you choose for your zappers have been tested and used for quite a number of years now, although not tested by the FDA. Most people are in agreement on the commonly used frequencies that are used in almost every "pad-type Rife" session. If you intend to use 465 hertz, for example, and the resulting frequency is actually 471 hertz, it is not going to work as intended. So, accuracy is very vital, as you stated.