Damn. This is rad.
607 karma · joined November 18, 2007
> We show that the digital signal that accompanies broadcast FM radio has sufficient structure to enable effective scheduling relative to it. It thus provides a common reference for neighboring devices to harmonize their transmissions, yet without requiring any explicit communication among them.
Monitorama PDX 2014 - Noah Kantrowitz
I couldn't find anything on Google to contradict that. Link?
It was also done in mainframes at the processor instruction level.