1     2     3     A  :  697 Hz
4     5     6     B  :  770 Hz(low tones)
7     8     9     C  :  852 Hz
*     0     #     D  :  941 Hz
----  ----  ----  ----
1209  1336  1477  1633 Hz
     (high tones)


or:


          1209 Hz 1336 Hz 1477 Hz 1633 Hz

                   ABC     DEF
697 Hz      1       2       3       A

           GHI     JKL     MNO
770 Hz      4       5       6       B

           PRS     TUV     WXY
852 Hz      7       8       9       C

                  oper
941 Hz      *       0       #       D


or:


    1  697+1209
    2  697+1336
    3  697+1477
    4  770+1209
    5  770+1336
    6  770+1477
    7  852+1209
    8  852+1336
    9  852+1477
    0  941+1336
    *  941+1209
    #  941+1477
    A  697+1633
    B  770+1633
    C  852+1633
    D  941+1633