A Disruptive Discharge Coil. Tesla's first high frequency coils looked remarkably similar to Violet Ray coils. This wire is as thin as a hair, and only occupies the center of the bobbin. Each layer must be heavily insulated from the next by pieces of waxed or varnished paper to prevent spark-overs and short circuiting. Different Violet Rays can be ran for longer periods of time than others due to better insulation of the resonator coil to prevent inefficiency and overheating.
Overheated coils produce weak sparks, and can eventually burn out.
Design characteristics were often the selling point of machines. The oscillator circuit consists of an electromagnetic interrupter that is used to rapidly charge a condenser to a high voltage and then discharge it through the primary of the disuptive discharge coil. This electromagnetic interrupter and condensers are essentially the same for all Violet Ray manufacturers. The one impossible goal for any collector is finding every single glass electrode made for these machines. Shelton Laboratories sold over 63 different electrodes.