Well I know absolutely nothing about electronics but my power panel sounds very similar. All I know is that it buzzes when connected to the plug and if I put a voltmeter on the outlets it shows 12 volts so I'd guessed that it's exactly what Rodney said, it pulses the power (I nearly said current but I figured the techo types would jump on that ).

However there's one thing to watch out for. Every plug needs a different setting to get the same heat in the coil. I like to have a dull orange glow because this is more than enough for easy starting without overheating the coil. Before I put a new plug in an engine I'll try it out first with the knob turned right down then slowly wind it up until it glows just right then note the position of the needle. I'm certain this is the reason for a lot of 4 stroke backfires and prop throwing...the power is turned up too high which advances the ignition timing.