It was brought to my attention that "Firematic" is most likely a brand name for the device I am talking about.
Problem is I do not know any other name for it.
It is essentially a heat detector with a single pole normally closed switch rated at 120 volts.
It is wired in series with the power supply to an oil burner in MA so that on temp rise the power to the burner will be cut off.
And now I am being told I need to install this for a gas fired furnace in RI.