Most people have heard of the "Three Mile Island" nuclear power plant accident of 1979. But it's famous among engineers for being a "normal accident", in that there wasn't any one thing that nearly caused a meltdown of catastrophic proportions...it was a series of little things inside a highly complex system that all happened as part of "normal" operations. None of which, by themselves, was terribly problematic. But they all happened at once, and that was a problem.
BOO! This time on the Engineer’s Corner, we’ll talk about PHANTOM POWER. Usually not as ghoulish as one might expect, phantom power has to do with microphones. Specifically, some microphones have active circuitry inside them. That means they need power to operate, but it’s unwieldy to run a separate power cord and audio microphone cable. So a phantom circuit is used to provide DC power on the same three wires (positive/hot, negative/cold, and ground) out to the microphone that the audio from the mic also uses.
A phantom circuit is one of those nifty things in electronics that looks, to the layman, like it can’t possibly work...but it does anyway.