[xnzakg]

Not sure how much I am allowed to go into detail here, but can confirm what 127361 wrote: the sensors harvest power from the electromagnetic field in normal use. However, considering "power outage detection" is a selling point, you can draw your own conclusions about there being some power storage onboard ;)

[bozhark]

power harvest and large/super caps? neat

[nomel]

I think the first assumption should be a boring old battery. Probably some lead acid type, since discharge would be very very rare.

[mistrial9]

probably patented by now? disclosed yet?