Touch Tone Telephone Exercises  
  1. Complete the table of frequencies shown in the Overview section.

    2.  
  2. MATLAB PROJECT. You need to use Matlab to solve this part. You will design a method to decode a phone number. For this purpose, you first need to download the file phone_number, which contains a signal that represents a phone number. Now go to the Matlab command window and type the command

      3. load phone_number

    We shall assume that this signal was generated under the following conditions:

        - Each digit is 800 samples long (and spans 0.097 second).
        - Each silence period between digits is 250 samples long (which corresponds to 0.0312 second).
        - The signal contains 10 digits (i.e., the area code is included).
        - The phone  number is within the (310) area code and every UCLA student knows it.

    In order to help you, here is some Matlab code to decode the first digit.


      >> load phone_number;
      >> soundsc(phone_number);
      >> signal1 = phone_number(1:800);
      >> psd(signal1,[],8192,[]);
      >> zoom on;

     
    Identify the two frequencies that correspond to these first 800 samples. Now repeat for the other digits until the phone number is identified completely.

  3. Most people do not dial their phone numbers with the precision assumed above (e.g., silence periods of equal duration or even digits of equal duration).  Modify your code and decode an irregular phone number (first download the file phone_number2).

      4. >> load phone_number2;
      >> soundsc(phone_number2);