Appendix

Tone Dial Frequencies

The tone dialing method combines two frequencies for each of the twelve digits found on a touch-tone dial pad. This method is referred to as dual-tone multi-frequency (DTMF) dialing.

The four horizontal rows on a touch-tone keypad use four low-frequency tones (697, 770, 852, 941 Hz), while the three vertical columns use three high-frequency tones (1209, 1336, 1477 Hz). The tone frequency tolerance is ± 0.02%.

For example, the digit 4 is dialed by combining two tone frequencies: 770 Hz from the second row, and 1209 Hz from the first column. In another example, the digit 9 is dialed with tone frequencies 852 Hz and 1477 Hz.

 

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1

 

 

2

 

 

 

3

 

 

A

 

 

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4

 

 

5

 

 

 

6

 

 

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7

 

 

8

 

 

 

9

 

 

C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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#

 

 

D

 

 

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1

 

 

 

2

 

 

 

 

3

 

 

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4

 

 

 

5

 

 

 

 

6

 

 

 

 

Figure B-2. Standard DTMF frequencies

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure B-3.

Extended DTMF frequencies

 

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7

 

 

 

8

 

Hz)

9

 

on some

The extended DTMF characters (A, B, C, D) are the high-end

frequencies

 

 

(1633

 

defined

telephone sets with a fourth vertical column of buttons. This fourth column provides for extended PBX control

 

 

 

 

 

 

 

 

functions. The actual functions that are provided depend on the

PBX

manufacturer’s

 

implementation and

feature set.

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Page 93
Image 93
Multi-Tech Systems MT2834MR6 manual Tone Dial Frequencies, Figure B-2. Standard Dtmf frequencies