noun: a device for automatically interrupting an electric current
"This seems to indicate that Keely used the resonant sphere, filled possibly with some gas, water vapor, water or some unknown chemical vapor, or in his carbon register accomplished the creation of high frequencies, much like Tesla later used an interrupter to create high electric frequencies. Through this means Keely hoped to produce complex alternating phases which would polarize and depolarize his disks in the magnetic engine." [Snell Manuscript]