Fascinating stuff.
As for electronics replacing mechanical systems Bosch K-Jetronic "constant flow" types (the injectors are not pulsed but produce a constant spray) work by "opening and closing the taps" using a combination of a sensor plate moving inside a cone in the intake for the gross adjustment modified by manifold vacuum, a bimetallic strip for warm up and an aneroid for altitude. My 1987 Mercedes has this "hydraulic control" on fuel and a completely separate electronic ignition system. With the advent of catalytic convertors, which are highly sensitive to air-fuel ratio, they added an electronic module to fine tune based on a lambda sensor output. A couple of years later they combined the ignition and injection into a single system.
http://en.wikipedia.org/wiki/Jetronichttp://www.auto-tat.co.uk/Bosch%20K-Jetronic.htmDavid