The development of microwave heating was preceded by work with radio waves, which were experimentally produced by Heinrich Hertz at Karlsruhe Polytechnic in Germany between 1885 and 1889. Hertz measured the wavelength and velocity of these waves. His first oscillator operated between 500,000 and 1,500,000 Hz (cycles per second), and the waves were tested on animals. He concluded that the only effect of these waves was that owing to heat. This work led to the first example of high-frequency heating therapy on humans at a Paris hospital in 1895.