a cloud during a thunderstorm. Uses Ignition sources Electric sparks are used in spark plugs in gasoline internal combustion engines to ignite fuel and air mixtures. The electric discharge in a spark plug occurs between an insulated central electrode and a grounded terminal on the base of the plug. The voltage for the spark is provided by an ignition coil or magneto that is connected to the spark plug with an insulated wire. Flame igniters use electric sparks to initiate combustion in some furnaces and gas stoves in place of a pilot flame. Auto reignition is a safety feature that is used in some flame igniters that senses the electrical conductivity of the flame and uses this information to determine whether a burner flame is lit. This information is used to stop an ignition device from sparking after the flame is lit or restart the flame if it goes out. Radio communications A spark-gap transmitter uses an electric spark gap to generate radio frequency electromagnetic radiation that can be used as transmitters for wireless communication. Spark gap transmitters were widely used in the first three decades of radio from 1887–1916. They were later supplanted by vacuum tube systems and by 1940 were no longer used for communication. The wide use of spark-gap transmitters led to the nickname "sparks" for a ship's radio officer. Metalworking Electric sparks are used in different kinds of metalworking. Electric discharge machining (EDM) is sometimes called spark machining and uses a spark discharge to remove material from a workpiece. Electrical discharge machining is used for hard metals or those that are difficult to machine with traditional techniques. Spark plasma sintering (SPS) is a sintering technique that uses a pulsed direct current that passes through a conductive powder in a graphite die. SPS is faster than conventional hot isostatic pressing, where the heat is provided by external heating elements. Chemical analysis The light that is produced by electric sparks can be collected and used for a type of spectroscopy called spark emission spectroscopy. A high energy pulsed laser can be used to produce an electric spark. Laser induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy that uses a high pulse energy laser to excite atoms in a sample. LIBS has also been called laser spark spectroscopy (LSS). Electric sparks can also be used to create ions for mass spectrometry. Spark discharge has been also