Apparatus adapted to distinguish between the presence of flame due to combustion of fuel discharged from a burner and the absence of the flame

Claim 1

IN COMBINATION, A COMBUSTION CHAMBER, A PLURALITY OF BURNERS EACH DISCHARGING A FLAME INTO SAID COMBUSTION CHAMBER WITH THE FLAME FROM EACH BURNER EXPOSED TO RADIATION FROM AT LEAST ONE OTHER BURNER, MEANS SUPPLYING FUEL TO SAID BURNERS, MEANS ASSOCIATED WITH EACH OF SAID BURNERS FOR DISTINGUISHING THE PRESENCE OR ABSENCE OF THEIR RESPECTIVE FLAMES IN THE PRESENCE OF FLAME DUE TO THE COMBUSTION OF FUEL FROM ONE OR MORE OTHER OF SAID BURNERS, EACH OF SAID DISTINGUISHING MEANS INCLUDING A MODULATING MEANS IMPARTING PULSES TO THE RADIATION OF ITS RESPECTIVE BURNER FLAME AT A PREDETERMINED FREQUENCY OTHER THAN THAT OF SAID OTHER BURNERS, RADIATION RESPONSIVE MEANS OPERABLY ASSOCIATED WITH SAID BURNERS AND ORIENTED TO SIGHT THE RADIATION OF SAID FLAMES TO PRODUCE A FLUCTUATING OUTPUT SIGNAL CORRESPONDING TO THE FREQUENCY OF THE RADIATION OF EACH OF SAID FLAMES, AND MEANS RESPONSIVE TO SAID RADIATION RESPONSIVE MEANS FOR DETECTING THE FLUCTUATING OUTPUT SIGNAL CORRESPONDING TO THE FREQUENCY OF THE RADIATION OF A GIVEN FLAME FROM THE OUTPUT SIGNALS CORRESPONDING TO THE RADIATION OF SAID OTHER FLAMES TO DISTINGUISH BETWEEN THE PRESENCE AND ABSENCE OF SAID GIVEN FLAME.