In 1928 Hollmann, von Willisen and Paul-Günther Erbslöh started a company Gesellschaft für elektroakustische und mechanische Apparate (GEMA).

By order of the German navy, in the summer of 1935 they developed a pulse radar with which they could spot the cruiser Königsberg at a distance of 8 km, with an accuracy of up to 50 m, enough for gun-laying.

Four units were ordered and installed on the Königsberg, Admiral Graf Spee and two large torpedo boats (which in German service were the size of small destroyers).

In December 1939, after heavy fighting during the Battle of the River Plate, the Admiral Graf Spee was severely damaged and the captain scuttled the ship in the neutral harbor off Montevideo, Uruguay.

These early-model Seetakt systems were followed in 1939 by a modified version known as Dete 1, operating between 71 and 81.5 cm wavelength (368 to 390 MHz) at 8 kW peak and a pulse repetition frequency of 500 Hz.