In the above schematic of a timing light made in the 60's by Heathkit, there is what amounts to an oscillator, a step-up transformer, a capacitor, and a xenon lamp. The xenon lamp fires when the high voltage from the car's distribution coil passes a threshold enough to establish rapid conductance, at which time the xenon effectively shorts the capacitor, creating a bright flash.
In this design, I can see where positive current comes in from the transistor's collector on the 'top' of the primary, and moves half-way down the primary to the grounded center tap. However, there is also the additional bottom half of the primary that ends up going through a capacitor and to the base of the transistor, no doubt to get it to oscillate.
My question: Is what's happening here that current is being passed through the top of the primary, and the bottom of the primary is simultaneously conducting, in opposite phase? Or, is a totally different phenomenon happening: is positive current coming down through C1 and C2, and entering the bottom part of the primary?
If the former, this throws my brain off a little because it makes intuitive sense that in the secondary-tapped transformer, all the input current is across the primary, and it is coupled entirely to the secondary magnetically, whereas in this case input current is placed across the top half of the primary, and must be magnetically coupled to both the secondary and the bottom part of the primary coil. (Correct?)
Another question: In either case, what are the specific purposes of C1, C2 and R3?