US Patent 3393279A Nervous system excitation device
a method of transmitting audio information to the brain of subject through the nervous system of the subject which method comprises, in combination, the steps of generating a radio frequency signal having a frequency in excess of the higherst frequency of the audio informattion to be transmitted, modulating said radio frequency signal with the audio information to be transmitted, and applying said modulated radio frequency signal to a pair of insulated electrodes and placing both of said insulated electrode in physical contact with the skin of said subject, the stretch of said radio frequency electromagnetic field being high enough at the skin surface to cause the sensation of hearing the audio information modulated thereon in the brain of said subject and low enough so that said subject experiences no physical discomfort.
