Abstract: A combustion technique and control is provided by the use of an optical pyrometer by means of which combustion control is afforded in accordance with the inspection of the combustion flame. The preferred optical pyrometer takes the form of an optical pyrometer having a single measurement cell which is alternately exposed to the flame through different filters arranged on a rotating disc driven by a motor. The circuit associated with the optical pyrometer, for purposes of generating control signals, features the use of a synchronous D. C. restorer which establishes a reference level for minimum signal distortion. Also employed is an AGC circuit by means of which one of the signals derived from one of the aforementioned filters is utilized to minimize undesired variations in the results. Gating logic is used to separate the two channels derived from the different filters and actually demultiplexes the two separate channels.