Track diagram, Berliner U-Bahn Museum
This track diagram is on the wall of the Berliner U-Bahn Museum. I'm not sure of its date, but quite a few stations have changed name since; Wikipedia suggests that the station name "Städtische Oper" dates this diagram to the 1929-1934 period.
The Berliner U-Bahn Museum is based in the former Olympia-Stadion signalbox. The museum is maintained by the Arbeitsgemeinschaft Berlin U-Bahn, and is normally open to the public on the second Saturday of each month.