The spark coil is a period-2 oscillator found in 1971. Despite its name, it does not produce sparks; however, the rotor resembles an electric spark.
Welded together with minimal separating stators, it can be extended indefinitely along its axis, so that it is the first in a series that continues with the piston and the long piston. It can also be arranged in two directions, as shown at Agar#Tile_agars.
Spark coil is the eleventh most common naturally-occurring oscillator in Achim Flammenkamp's census, being less common than the figure eight but more common than the mold.
- 18P2.28 at Heinrich Koenig's Game of Life Object Catalogs