Chuck, that's a good description of the traditional coil/condenser/breaker points ignition. That circuit is a bit more exotic than it appears. The ignition coil has significant self-capacitance in its windings, which the external capacitor (typically .25 microfarad) matches, so it generates a damped sine wave in the coil primary and a much higher voltage than the supply voltage for a few cycles. The basic design came from spark transmitter ringing circuits in early radio (ca. 1910). A couple of big names in applying the circuit to ignition systems were A(rthur) Atwater Kent and Charles Kettering (Delco).
What is important to realize, when diagnosing problems, is that the external capacitor has a major function in generating the high voltage spark after the ignition points open. A failing capacitor often shows up as afterfiring in the exhaust---engine skipping and giving a lot of snap-crackle-pop in the exhaust.
I have wondered about the later Onan setup on the Deere tractors, with an electronic switch, but including a capacitor at the 12V supply terminal.
In the traditional Delco mechanically-switched circuit, a capacitor was mounted on the supply terminal to suppress radio frequency noise in car radios. Why Onan/Deere felt one was needed in an electronically-switched system, I don't know. But as Chuck has pointed out, somebody had to make a case to force the cost engineers to include it.
There may be some confusion about "condenser" vs. "capacitor." When applied to these electrical devices, they are synonymous; i.e., a "condenser" is a capacitor. The term "condenser" was standard in American-speak for all electronic applications until the 1950's, but has continued to live on in the automotive applications.
Hank
