Secondary Ignition: The Art Of Spark
by Scott Weaver
This article describes the components of a conventional distributor ignition system, and how they produce a spark. Scott also shows what a (secondary coil) ignition waveform looks like, and describes its different parts.
Maintaining Engine Spark
by Mac Vandenbrink
An explanation of how to use the ignition pattern/waveform to detect a coil fault, turbulence problem, or even an injector issue.
Coil on Plug Ignition: The Wired Differences
by Matt Dixon
An explanation of the different types of coil-on-plug modules, how they work, and how they can fail.