6 8 D O C U M E N T 5 7 A U G U S T 1 9 2 5 57. To Hermann Anschütz-Kaempfe Berlin, 31 August 1925 Dear Mr. Anschütz, The sailing-filled vacation time is now over. It was nice and I cannot thank you enough for the wonderfully pretty haven you have created for me in Kiel. Albert is working very hard. I think it would also give you pleasure to observe him. He was also the main reason why I thought about how possibly to produce a transmis- sion without rubbing contacts. For this I now have a solution that I am persuaded is superior to Siemens’s. I pass it on to you herewith and ask you please to give me your opinion of it, mainly also with regard to its applicability to the gyro compass. I. A, B, and C are a number of stators with three-phase windings. They are con- nected in parallel, as the figure indicates. Then they are magnetically coupled, so that the same alternating-current magnetic fields must always form in all three, irrespective of how the current is supplied. II. A is a stator with three-phase winding that is fed by a rotary current. Then a rotating field forms in A that is equally strong in all directions. If I in- sert an iron rotor α , that is set in a par- ticular direction, then the magnetic resistance is much reduced in this direc- tion. If I don’t supply it with a given potential, but with a given current, which I can force at a given potential by connecting self-inductions s in series that devour most of the terminal voltage, then a rotating field forms whose field is much stron- ger in the direction of rotor α than in the direction perpendicular to it. III. Let ¢rotor² stator A be the first among the stators of I. Through α its field will prefer the direction of α , and this influence is transmitted by the magnetic coupling to the stators B and C. If they also have rotors, then they set themselves in parallel. Therefore, the rotors are ¢electrically² magnetically coupled.