The invention provides a double ended thyratron arrangement in which at each end of the thyratron there is a cathode, at least one intermediate grid and a final grid which borders a high voltage withstanding gap. At each end of the thyratron the final grid which borders a high voltage gap is connected to act as a screen electrode, usually by connecting this grid directly to the cathode. At the same time, at one or both ends of the thyratron means are provided for applying triggering input pulses to one of the intermediate grids between the respective cathode and final grid. The thyratron may be of the pentode type, in which case, at each end the final grid is connected to act as a screen, the intermediate grid adjacent the cathode is subject to bias and the triggering signals are applied to the intermediate grid adjacent the final grid.