File:Tesla's glow lamps.jpg

English: Glow lamps, similar to neon lights, invented by Nikola Tesla and powered by one of his compact Tesla coils. The lamps, consisting of partially evacuated glass tubes with electrodes at either end, are similar to Geissler tubes , invented in 1857 by Heinrich Geissler. During the 1890s Tesla worked on developing a "wireless" room lighting system. Although in this example the tubes are powered by wires, Tesla showed they could be powered without wires from a high potential high frequency electric field created by a nearby Tesla coil. A technical article describing how this type of compact Tesla coil works and giving circuit diagrams is "Tesla circuit controllers for obtaining oscillatory currents of high frequency" in The Electrical Engineer, New York, Vol. 26, No. 538, August 25, 1898, p. 180-182

Caption: This illustration shows one of Tesla's high frequency generators and a bank of his high frequency lamps lighted by the same. These highly evacuated, gas-filled tubes were operated in different ways. In some cases they were connected to one wire only, in others to two wires in the manner of ordinary incandescent lamps. Often, however, they were operated without any connection to wires at all, i.e. by "wireless energy", over quite appreciable distances, which could have been greatly extended with more power. The oscillator comprises a Tesla high potential transformer which is excited by a condenser and circuit controller, as described in his 1895 patents. The primary exciting element comprised a powerful electro-magnet actuating an armature, and this was supplied with 110 volt 60 cycle current. When the oscillator was put into operation, the interrupter actuated by the electro-magnet connected to the 110 volt circuit became simultaneously the spark gap for the high potential exciting circuit, which included the vibrator, spark gap, high tension condenser and primary of the high frequency Tesla transformer. The lamps were connected to the secondary of the latter, whose terminals can be seen at the rear of the machine.