interrupter was invented by Rev. Prof. James William MacGauley (1838) of Dublin, Ireland, Johann Philipp Wagner (1839), and Christian Ernst Neeff (1847). Hippolyte Fizeau (1853) introduced the use of the quenching capacitor. Heinrich Ruhmkorff generated higher voltages by greatly increasing the length of the secondary, in some coils using 5 or 6 miles (10 km) of wire and produced sparks up to 16 inches. In the early 1850s, American inventor Edward Samuel Ritchie introduced the divided secondary construction to improve insulation. Jonathan Nash Hearder worked on induction coils. Callan's induction coil was named an IEEE Milestone in 2006. Induction coils were used to provide high voltage for early gas discharge and Crookes tubes and other high voltage research. They were also used to provide entertainment (lighting Geissler tubes, for example) and to drive small "shocking coils", Tesla coils and violet ray devices used in quack medicine. They were used by Hertz to demonstrate the existence of electromagnetic waves, as predicted by James Clerk Maxwell and by Lodge and Marconi in the first research into radio waves. Their largest industrial use was probably in early wireless telegraphy spark-gap radio transmitters and to power early cold cathode x-ray tubes from the 1890s to the 1920s, after which they were supplanted in both these applications by AC transformers and vacuum tubes. However their largest use was as the ignition coil or spark coil in the ignition system of internal combustion engines, where they are still used, although the interrupter contacts are now replaced by solid state switches. A smaller version is used to trigger the flash tubes used in cameras and strobe lights. See also Ignition coil Trembler coil Spark gap transmitter Transformer Tesla coil Faraday's law of induction Ignition system Inductor Magnetic field Nicholas Callan Footnotes Further reading Norrie, H. S., "Induction Coils: How to Make, Use, and Repair Them". Norman H. Schneider, 1907, New York. 4th edition. Has detailed history of invention of induction coil External links Battery powered Driver circuit for Induction Coils The Cathode Ray Tube site Relay Technical Information See section "Contact Protection – Counter EMF". Capacitive Discharge Ignition vs Magnetic Discharge Ignition: Ignition System Options for the TR4A See figure 9 for actual discharge. Electric transformers Electrical breakdown