This is the old logomark of the joint venture company created by Siemens Co. and Furukawa Electric Co. (It contains the S from Siemens Co. and the F from Furukawa Electric Co.)
This logomark is the product logo mark of PROTOS, a home appliance product of Siemens Co. (The double S originates from Siemens-Schuckert.)
The Logomark of Fuji Electric Industries.
This logomark of Fuji Electric Industries was created by combining the best parts of the former two logomarks.
A vacuum cleaner with the PROTOS logomark. (It was widely understood that products bearing the PROTOS logo were not only useful, but dependable, sturdy and did not malfunction.)
Werner von Siemens, the founder of Siemens Co.