Metox radar detector

FuMB-1 Metox - This rudimentary antenna consisted of five pieces of wood tied together into a cross, with wires wrapped around it. It was installed into a bracket on the conning tower and periodically was rotated by hand. British photographs of the antenna led to their nickname, "Biscay Cross".

The R600A Metox, named after its manufacturer, was a pioneering high-frequency radar warning receiver (RWR) used by the German forces on U-boats from 1942-45. It was initially installed to receive signals used by British radars.