HotRod,
yes, that is how they work. The primary has a center tap which is connected to ground. The vibrator alternately applies 6 v to each side of the winding.
An interesting thought is how they did this before the mechanical vibrator. The early auto radios used a motor generator set to accomplish this. I can't recall the name for that arrangement.
I get the impression that the military provided some pretty good training while on the job.
