circuit containing the detector. A radio system with a "two circuit" (inductively coupled) transmitter and receiver was called a "four circuit" system. The first person to use resonant circuits in a radio application was Nikola Tesla, who invented the resonant transformer in 1891. At a March 1893 St. Louis lecture he had demonstrated a wireless system that, although it was intended for wireless power transmission, had many of the elements of later radio communication systems. A grounded capacitance-loaded spark-excited resonant transformer (his Tesla coil) attached to an elevated wire monopole antenna transmitted radio waves, which were received across the room by a similar wire antenna attached to a receiver consisting of a second grounded resonant transformer tuned to the transmitter's frequency, which lighted a Geissler tube. This system, patented by Tesla 2 September 1897, 4 months after Lodge's "syntonic" patent, was in effect an inductively coupled radio transmitter and receiver, the first use of the "four circuit" system claimed by Marconi in his 1900 patent (below). However, Tesla was mainly interested in wireless power and never developed a practical radio communication system. In addition to Tesla's system, inductively coupled radio systems were patented by Oliver Lodge in February 1898, Karl Ferdinand Braun, in November 1899, and John Stone Stone in February 1900. Braun made the crucial discovery that low damping required "loose coupling" (reduced mutual inductance) between the primary and secondary coils. Marconi at first paid little attention to syntony, but by 1900 developed a radio system incorporating features from these systems, with a two circuit transmitter and two circuit receiver, with all four circuits tuned to the same frequency, using a resonant transformer he called the "jigger". In spite of the above prior patents, Marconi in his 26 April 1900 "four circuit" or "master tuning" patent on his system claimed rights to the inductively coupled transmitter and receiver. This was granted a British patent, but the US patent office twice rejected his patent as lacking originality. Then in a 1904 appeal a new patent commissioner reversed the decision and granted the patent, on the narrow grounds that Marconi's patent by including an antenna loading coil (J in circuit above) provided the means for tuning the four circuits to the same frequency, whereas in the Tesla and Stone patents this was done by adjusting the length of the antenna. This patent gave Marconi a near monopoly of syntonic wireless telegraphy