A violet ray is an antique medical appliance used during the early 20th century in the obsolete medical therapy called electrotherapy. Their construction usually feature a combination of a disruptive discharge coil with an interrupter to apply a high voltage, high frequency, and low current to the human body for therapeutic purposes. Their basic construction was invented by Nikola Tesla prior to 1900, who introduced their first prototypes at the World's Columbian Exposition in 1893. Most of the antique violet rays in the US were produced before the Depression era and some of the larger US manufacturers of violet rays were Renulife, Fitzgerald and Fisher. Companies who manufactured violet ray devices, made many other types of electrical appliances as well, e.g. Star Electric, which also manufactured stock ticker machines. Many of the companies who were able to continue manufacturing violet rays after the depression, stopped making them due to World War II when they began manufacturing radio coils or other electrical components for the war instead.
A typical violet ray device consisted of an ungrounded electrical control box that controlled the interrupter and which housed the magneto coil, and an attached bakelite or other handle housing which contained the high voltage coil and an insertion port for attachments. Glass evacuated tubes of varying shapes and for different therapeutic uses could be inserted into the bakelite handle to apply the resulting current to different parts of the body.