The Solenoid Robots, who talk in barely understandable electronic voices
The robot is controlled by a computer running the Linux operating system and HexEngine software, which controls the hydraulic solenoid in the legs.
The solenoid-controlled metering rods allow the fuel mixture to be very close to optimum, then the solenoid is pulse width modulated at about 6 Hz to fine-tune the air fuel ratio under closed loop conditions.
The final complete system came in 1927 when Berlin-based Max Ruhl and Ernst Neuman combined internal illumination and solenoid operation.