The continuous pulse protocols (1, 2, 3, 4, 5, and 10 pps) have been used from the very beginning of ICES research, and continue to be used in controlled scientific studies, such as the 2017 Cortical Metrics – TBI study:
Many people simply want to experiment with steady, continuous pulse trains, so this is a good set of common frequencies to start with.
The model M1 can generate a several constant output pulse frequencies. For most applications I recommend the use of one of the four standard protocols (B5-C5, P2, A9, Omni-8) to avoid tissue accommodation which can reduce the tissue response over time if a stimulus signal is monotonic and unchanging.
The list has the most commonly used single frequencies, including:
Some people have good scientific reason to believe that one or more of these specific pulse frequencies may be of benefit for specific applications. As a scientist I remain skeptical, and I am not a clinician, so I can not give specific advice on which frequencies to use for which condition.
Using the model M1 you may experiment for yourself.