Frequency                                                   
                                                                
    120 +  *                                                    
        |  *                                                    
        |  **                                                   
        | ***                                                   
     90 +*****                                                  
        |*****                                                  
        |*******                                                
        |*******                                                
     60 +*******                                                
        |*********                                              
        |*********                                              
        |*********                                              
     30 +************                                           
        |************   *                                       
        |**************** *                                     
        |***********************  * *                           
        ---------------------------------------------------     
         1234567891111111111222222222233333333334444444444>     
                  0123456789012345678901234567890123456789=     
                                                          5     
         PPQ M  MQ                                        0     
         511 e  e3      P     P                                 
          0  d  a       9     9                                 
             i  n       0     5                                 
           M a                                                  
           o n                                                  
           d                                                    
           e                                                    
                                                                
                             X Midpoint