Ventless heater O2 depletion sensor question

[ZZonka Tonka]

I was installing a used ventless heater and was looking at the manual online, I'm wondering how the oxygen depletion sensor works? All it looks like is a couple of metered holes in the pilot line feed line? It looks like if the O2 level drops the pilot light does not burn hot enough to keep the thermal couple hot enough to keep the gas safety to the pilot light from shutting off? Is this all there is to the O2 depletion sensor? A couple of metered holes?

[HeatMan]

That's the way I understand it.

That's also the reason I won't have one of those style heaters.