"Back to 3554 Hz. Dr. R.R. Rife specified that any frequency needed to be within 0.05 percent of the true MOR. That means that according to Rife, if the frequency is more than 1.777 Hz off at 3554 Hz then the results will be significantly reduced. It does not mean completely ineffective, just reduced. However, the further off that a frequency is, the effectiveness is increasingly reduced."
Or if you have a mutated version of the pathogen that has a slightly different MOR frequency. Some of the machines drift as they warm up which can be an advantage. More advanced generators have a sweep feature that allows them to drift in a planned controlled manner.
If you don't want to program it yourself, deal with high tech devices. Then this device would be a good choice.
Of course you could just use the exact Beck Protocol for best results.