There is a gap in the ionosphere of the Earth's atmosphere. It creates a massive electronic cavity in which a certain frequency can resonate constantly, as a sort of "signature" of this planet. That frequency is generally given as 7.83 cycles per second. According to some researchers, it may change over time. Several inventors have developed devices which are worn close to the body and constantly impart this frequency to a person, using the theory that having this "correction" in a person's biofield will create a defense against unnatural electromagnetic fields.