When the appeared the first Medical Coils , for small areas of the body, were used the toroidal coils.
On the Internet they have been christened "bagels". They were small in size and easily applied to the face.
The first Healing Coils were made one the flat and one the torus.
As a result of numerous experiments, it was found that the Healing Coils, made in the form of Thor, do not give a healing effect.
The therapeutic effect is only under the turns of the wire. Consequently, the most effective Healing Coils are flat, with winding from the center point.
The required diameter of the coils is achieved by the diameter of the wire.
The spatial form of the radiated field is formed and focused by a system of coils. Their mutual adjustment and location in the instrument housing. Usually 2 - 4 spaced, tuned and fixed coils.
An additional, and very good therapeutic effect, gives a combination of frequencies using a microcontroller.