Electronic control of the combustion process is the primary reason the Lynndale System leads the market in effeciency. The top arrow to the left points to the fan & limit control mounted above the unit in the plenum.
When the thermostat located in your home calls for heat, the primary combustion air blower (bottom arrow to left) ignites the coals in the firebox, raising the temperature in the plenum. When it reaches 120 degrees F, the warm air distribution blower is activated and moves heated air into the home.
When the temperature climbs to 140 degrees, the limit control cuts out the combustion air blower, returning the wood in the firebox to a smoldering state. This not only conserves wood but it also prevents overheating your home.
The main blower continues to deliver heated air to the home until the thermostat setting is reached. A second control, the fan override, will activate the main blower to remove excess heat if you forget to close the ashpit door.

The close up shot of the fan & limit control to the right shows the probes that sense the temperature directly above the firebox.
One probe controls the primary combustion air blower and the other regulates the operation of the warm air distribution blower that moves the heated air into the home.