Abstract: A system for determination of presence of flames is provided. The system includes a photosensitive transducer configured to generate a response signal that is a function of electromagnetic radiation from a flame source. The system also includes a signal processing unit that includes a modulation unit and a demodulation unit. The modulation unit is configured to generate a modulated response signal by modulating the response signal with a modulation signal of frequency higher than that of an unwanted signal present the response signal. The demodulation unit is configured to determine an output signal by demodulating the modulated response signal. The demodulation unit eliminates the unwanted signal from the modulated response signal during the determination of the output signal. Further, the system also includes a processing unit configured to process the output signal to determine flame presence based on the intensity of the incident radiation from the flame.