Time and technology have advanced the mechanical to electric.
I have two electic foot pedals which probably do the same thing as the Fotdella.
The first one I acquired was like a one-octave (12-note) pedal keyboard (like a church organ pedal system) which plays through its own (tube) amp and speaker box.
I later found a similar one-octave Roland Bass Pedal board that simply sends a MIDI signal to a synthesizer whereby you can produce all kinds of sounds, including bass.