On 16 December 1947, "Using this double point contact, contact was made to a germanium surface that had been anodized to 90 volts, electrolyte washed off in H2O and then had some gold spots evaporated on it. The gold contacts were pressed down on the bare surface. Both gold contacts to the surface rectified nicely... The separation between points was about 4x10−3 cm. One point was used as a grid and the other point as a plate. The bias (D.C.) on the grid had to be positive to get amplification... power gain 1.3 voltage gain 15 on a plate bias of about 15 volts".