Electrical direct current is the flow of electrons from the negative pole to the positive pole. When using a 100% offset, if you have an electrode on each of your hands, electrons will flow from one electrode to the other at a certain rate (the freq you're using).
If you use a 0% offset and a simmetrical waveform, then, the flow of electrons will change its direction at a certain rate (the freq you're using).
In both cases, the result is that for every electron that entered your body, another electron exit, so the total charge remains the same as before the session.
In terms of electrical charge, no matter if the electrons enter through your right hand and exit trough your left hand, or vice versa, so, polarity doesn't matter in contact mode, because your liver doesn't care if the current it's receiving comes from the left or the right. It is only electrons flowing.
If you use plasma, or laser, or remote, things are different. these devices only have two states, 0 and 1. The plasma bulb hasn't a negative state. It is on or off, so you can't use alternating current to drive it. That's why you need a 100% offset to drive SC., and -100% offset to run the lasers (the negative sign is because the electrical wiring).
The remotes can accept 0% offset because they have a section which "lights" for the positive current, and another one for the negative current. If you use a -100% Offset, it is exactly the same as if you use 100% offset with the remote. The nail is receiving the freqs through the positive coil or through the negative one . the nail doesn't know about up and down, so it can't tell the difference between the two coils. All this must be nuanced for the remote with magnet, that has already a polarity.
In a remote, if you use 0% offset, what you get is simply double the frequency you're sending to it. If your remote has a magnet, also half the freq you get is in the "wrong" direction. That's why the BN and MN ports on the Boost, just to match the different polarities of the two remotes.
All this, however has an extreme importance when using a PEMF coil, because there are present electromagnetic fields, that have a polarity, and that polarity, if right, is what helps to heal. I would never use alternating polarity when driving a coil, and would choose the polarity according to the already proven magnetic therapy you mentioned.
Hope my point of view helps you to clarify your doubts.
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