Section 6 – VC-20™ ATC-10b Vocoder Board Advanced Features
VC-20
ATC-10b Vocoder Board User’s Manual
page 12
The Speech Compression Specialists
D
IGITAL
V
OICE
S
YSTEMS,
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NC.
3.7
VC-20-ATC-10b DTMF Tone Data
The VC-20-ATC-10b supports DTMF detection, transmission, and generation. The
encoder detects and transmits DTMF tones, and the decoder decodes and generates
DTMF tones, in support of standard telephony requirements
In addition, if the VC-20™ - ATC-10b encoder detects a DTMF tone it activates the
DTMF_DET signal for four clock cycles of TXCK and simultaneously outputs (LSB first)
four bits of data on DTMF_DAT which identify the DTMF tone which was detected.
The DTMF_DET flag is only output once for each continuous DTMF tone that is
detected. The correspondence between the data bits and DTMF tone is shown in Table
1.
DTMF_DAT
Keypad Character
MSB…LSB
Freq #2
Freq #1
1
0000
1209 Hz.
697 Hz.
4
0001
1209 Hz.
770 Hz.
7
0010
1209 Hz.
852 Hz.
*
0011
1209 Hz.
941 Hz.
2
0100
1336 Hz.
697 Hz.
5
0101
1336 Hz.
770 Hz.
8
0110
1336 Hz.
852 Hz.
0
0111
1336 Hz.
941 Hz.
3
1000
1477 Hz.
697 Hz.
6
1001
1477 Hz.
770 Hz.
9
1010
1477 Hz.
852 Hz.
#
1011
1477 Hz.
941 Hz.
A
1100
1633 Hz.
697 Hz.
B
1101
1633 Hz.
770 Hz.
C
1110
1633 Hz.
852 Hz.
D
1111
1633 Hz.
941 Hz.
Table 1: DTMF Tone Data
