# Detecting DTMF Tones with MATLAB Function

## Introduction to DTMF Detection

## Steps to Detect DTMF Tones

**1. Define the Function:** Begin by defining the MATLAB function "DTMFDetector" with x, N, sampleRate, and duration as inputs.

**2. Calculate Number of Samples:** Determine the total number of samples, "numSamples," using the sampleRate and duration parameters.

**3. Create Empty Vector:** Initialize an empty vector, "number," to store the detected digits and characters.

**4. Iterate Over Signal:** Use a for loop to iterate over the input signal, x, in blocks of length N.

**5. Apply Discrete Fourier Transform (DFT):** Utilize the "fft" function to apply the DFT to each block of the signal.

**6. Compute Magnitude Squared:** Calculate the squared magnitude of the DFT coefficients, |X[k]|^2, using abs() and ^2 operations.

**7. Identify Maximum Magnitude:** Determine the maximum magnitude squared value for each DTMF tone frequency (697 Hz, 770 Hz, 852 Hz, 941 Hz, 1209 Hz, 1336 Hz, 1477 Hz).

**8. Determine Detected Tone:** Based on the identified tone frequencies, determine the corresponding digit or character.

**9. Append Detected Digit:** Add the detected digit or character to the "number" vector.

**10. Return Output:** Finally, return the "number" vector as the output of the function.