This tube, made in Germany by an unknown maker, and judging from the DRGM and DRP (German patent) numbers, goes back to around 1908. Its function is based on the principle of the important size asymmetry of the electrodes, with the current flowing more easily in one direction than in the other.

                   The tube terminal connections are respectively marked with a + and a - sign, the (+) side being connected to the small rod-type electrode, visible on the left, in the axis of the large cylindrical electrode (see x-ray picture) connected to the (-) terminal.

                    The tube is 14”(35cms) long, with an 8”(20cms) bulb, slightly flattened in its longitudinal axis. It is equipped with a condenser-type regeneration device consisting of two semiconductor cylinders separated by a dielectric material (see x-ray picture), and connectable to the tube terminals.