The document discusses methods for detecting Dual-Tone Multi-Frequency (DTMF) signals. It compares the Direct Fourier Transform (DFT) method, Fast Fourier Transform (FFT) method, and Goertzel algorithm for calculating the DFT. The Goertzel algorithm reduces arithmetic operations compared to the DFT and FFT for certain applications. The document also proposes improving DTMF detection by varying the number of samples analyzed between 80-85 instead of a fixed number, to further reduce computations.