I'm confused. It looks like they're selling battery and wired versions of the device, and the wired version also contains a battery backup (according to the spe

I'm confused. It looks like they're selling battery and wired versions of the device, and the wired version also contains a battery backup (according to the specs page - click "Show Detailed Specs" and it says it comes with "Three long-life backup batteries"): https://store.nest.com/product/smoke-co-alarm/ https://store.nest.com/product/smoke-co-alarm/