Signedon orange sticker on side of metal base: WESTINGHOUSE / THYRATRON TYPE / TYPE KU-676
FunctionThyratron are rectifiers based on a design similar to a triode vacuum tube, but which work with a rarefied atmosphere of noble gases, mercury vapor or hydrogen. As a triode amplifier, it has a heated cathode, an anode or plate, and a control grid.
In the case of thyratrons, when the voltage between the hot cathode and the anode is positive, and the grid is also positive with respect to the cathode, the gas in the bulb ionizes and an electric arc extends from the cathode to the anode transmitting current. When the grid is at the same or lower voltage than the cathode, the electric fields are not strong enough to ionize the gas and there is very little current flow. However, once an electric arc is established, even if the grid voltage is lowered, current will continue to flow until the voltage between cathode and anode is lowered (for this reason they cannot be used as amplifiers).