As the head of the research workshop of the Deutsche Reichspost in the winter of 1936/37, Otto Dunkel applied himself to building the first ionospheric transmitter that would allow information to be beamed into the high atmosphere so that it could be reflected and received in a different place. The tests to transmit information between Berlin and locations in Spain and Italy did not run smoothly. There were big problems with the contact plugs of the transmitters. The models which were common on the market did not permit a uniform contact resistance. Otto Dunkel pondered over how this issue could be solved.
In the end, it wasn‘t scientific investigations which helped him, but his own power of observation and imagination: “It must have been in 1937, I was standing at my window and looking out into the courtyard of the Reichspost’s central office. I was quite upset because I wasn‘t making any progress. Then I saw a man in the courtyard sweeping up the leaves with a broom made of brushwood. That gave me the idea for a new contact. My point of view was now this: It is impossible to create contact between two level surfaces which always lie flat against the whole surface and therefore always have the same contact resistance, and also the same contact pressure. So my thoughts were: Why not divide the contact into lines just like the inventor of the brushwood broom had done with the individual twigs? That is how the new contact came to be.”
This springwire contact is the first in a long line of inventions by this company, the first patent, the nucleus of a remarkable success story in the German middle class – and still one of the most important products in the portfolio of ODU. To this day nothing about the brilliant construction principle has fundamentally changed. And rightly so: because it still guarantees low contact resistances, a large number of independently flexible contacts, an extremely secure connection, high current carrying capacity, high vibration stability and a very high number of mating cycles of 100,000 and more. Some customers even report over one million mating cycles.