Just as every radio channel has its own frequency, so every cell and organ in the human body has its own distinct wave frequency. These frequencies can be measured and compared with the frequencies of healthy tissue, which have been stored in a databank that has compiled standards based on age and gender. This allows for comparison with frequencies of healthy tissue and isolate known and confirmed anomalies of diseased or unbalanced tissue…

This quote from Wikipedia:

“Bioelectromagnetics, also known as bioelectromagnetism, is the study of the interaction between electromagnetic fields and biological entities. Areas of study include electrical or electromagnetic fields produced by living cells, tissues or organisms, including bioluminescent bacteria; for example, the cell membrane potential and the electric currents that flow in nerves and muscles, as a result of action potentials. Others include animal navigation utilizing the geomagnetic field; potential effects of man-made sources of electromagnetic fields like mobile phones; and developing new therapies to treat various conditions. The term can also refer to the ability of living cells, tissues, and organisms to produce electrical fields and the response of cells to electromagnetic fields”

 
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To learn more of this please visit Wikipedia and search for the following terms:
Electromagnetics
Bioelectromagnetics
Electrophysiology
Biofield

The ETA-Scan is used as widely in Europe, where there are over 3,000 practitioners utilising it on a regular basis to better determine the health status and potential of their patients.