       7   6   5   4   3   2   1   0   7   6   5   4   3   2   1   0   7   6   5   4   3   2   1   0   7   6   5   4   3   2   1   0
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0000 | DTMF number 0                                                                                                              ...
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000c  ...                                                                                                                            |
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0010 | DTMF number 1                                                                                                              ...
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001c  ...                                                                                                                            |
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      ...                                                                                                                         ...
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00f0 | DTMF number 15                                                                                                             ...
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00fc  ...                                                                                                                            |
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