an arrangement of two electrodes between which a disruptive discharge or electricity may take place, and such that the insulation is self restoring after the passage of a discharge

The distance between the electrode and the workpiece when discharges are occurring.

Electrical apparatus used for the production of repeated spark discharges between the two or more electrode s forming the system; a transmitting device for generating radio frequency ( R.F.) waves, commonly used in early wireless transmitter. Remained in popular usage until the advent of the Multiple Tuner and Magnetic Detector combination around 1908. The first demonstrations of practical radio communication, both by Marconi and others, were carried out using spark gap transmitter

A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air. When a suitable voltage is supplied, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the 'holding current'.