In Model A we have stayed true to the engineering model that assumes the sharper the square wave, the more effective it will be. Within reason. It also amplifies the danger signals to the user that something is wrong, or too powerful. Those signals are manifest on the surface, where they are felt more sharply, leading to the user reducing their amplitude.
Model A output signal is configured in a specific way, for important reasons. One of the reasons is to help contain and control any potential injury from the effects of current.
Ordinarily, the user has no stinging sensation. The amount of power they can comfortably tolerate is limited by the quality of the connection, and the size of the contact areas. The configuration of the signal tries to anticipate a standard size and quality of contact.
The standard is not present if the areas of contact are made larger than the amount of concentration of energy it takes to cause electroporation on the skin.
Using a standard size patch, as the frequency of the recording changes, the sensation will also change. The user only perceives a pleasant tingle, and adjusts the amplitude to keep the sensation at that comfort level throughout the session.
The way it feels to the user provides natural limits on the extent of the therapy any home user might perform on themselves.
Slight redness under the patch after a session is normal.
The transfer of current in high enough concentrations however, can cause stinging on the skin tissue under the patch. It is the same effect that can cause an electric burn, called electroporation.
Model B output signal was created with much older design and components. The Model B configuration mostly directed the same effects past the skin. This caused far less stinging sensation on the skin.
In each case the same amount of energy was applied, resulting in the same amount of electroporation, but manifest slightly differently.
It is believed at this point that if electroporation is going to occur in any amount it is best if it appears in a prominent place, so it draws attention immediately.
If it occurs deeper, in the blood vessels or the nerves, the extent of that electroporation is not perceived, and cannot be easily assessed. Therefore the Model A signal configuration is believed to be safer, more intuitive and more effective overall.
A slight stinging sensation on the skin under the patch is common. Unusually strong stinging or burning effect may indicate nerve and blood vessel problems, fungal infections, and may be very aggravated by a poor connection either on the skin, or at the lead-pins.
Sometimes, only the tiniest amount of current can be tolerated. This will often change over time, as the user progresses. In some areas of the body, obviously, only a tiny amount of energy should ever be applied, such as the head and groin.