CuriousGeorge said:
Are there non-traditional systems that do NOT use the cap/rotor system, and if so, how do THEY work?
Yes, of course. Many, if not most modern cars are so equipped. Basically they use an ignition coil for every cylinder, or every pair of cylinders.
The coil-per-cylinder approach is obvious ... to use one coil for a pair of cylinders takes a special coil that has both ends of the secondary (high voltage) winding brought out to plug leads. In that case (known as a "waste spark" system), both plugs always fire together, but one of the cylinders is between intake and exhaust strokes where the spark has no effect.
Not sure offhand how long "waste spark" systems have been in common usage, but I owned a 1965 Honda motorcycle that used it. 2 cylinders, no distributor. Points rode right on the crankshaft.
There are even kits available to retrofit older motors with distributorless ignition, but they tend to be rather pricey and need to be custom-tuned to your engine. Without the distributor to determine the spark advance, they use electronics instead. Also require a crank position sensor so the electronics can figure out what's happening when.