Diathermy treatment of spine using condenser pads in 1945. Diathermy is the application of radio frequency current to body tissues to cause deep heating. In this example two metal plate capacitive electrodes are placed on the back, with insulating pads separating them from the skin, and the high frequency current from the diathermy machine applied between them. Each electrode acts as one plate of a capacitor, with the body tissue under it as the other plate. The high oscillating potential between the plates induces an alternating current to flow through the body tissues between the plates, warming them.