BNC 630 - Manual (Page 33)

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5.16 DTMF Generation Mode
Introduction
The DTMF (Dual Tone Multi Frequency) Generation mode generates the Touch-tone dialing tones for the American telephone
network. The user can specify dialing digits "0" to "9", "
∗
", "#" as well as the extra DTMF digits "A" through "D".
A start delay can be specified for each digit. The duration of each digit can also be specified. These two parameters make it
possible to test the performance DTMF detection systems. By sending a string of digits to dial to the RS232 port, the 630 can be
used as a speed dialer; these digits are queued and dialed with the specified duration and delay between digits.
Note: The 630 can generate a single DTMF digit on a repetitive basis by switching to Dualtone Generation mode and setting each
dualtone frequency to that of the desired DTMF digit. The ON and OFF times can then be set to repetitively generate the digit for the
desired duration and repetition rate. Refer to the chapter on Dualtone Generation mode for more information.
Background
A DTMF dialing tone consists of two sinusoids of different frequencies which are added together to form the output waveform.
These frequencies were chosen so that they are not harmonically related. The table below lists each dialing digit and its associated
dualtone frequencies:
DTMF 0: 941 Hz and 1336 Hz
DTMF 1: 697 Hz and 1209 Hz
DTMF 2: 697 Hz and 1336 Hz
DTMF 3: 697 Hz and 1477 Hz
DTMF 4: 770 Hz and 1209 Hz
DTMF 5: 770 Hz and 1336 Hz
DTMF 6: 770 Hz and 1477 Hz
DTMF 7: 852 Hz and 1209 Hz
DTMF 8: 852 Hz and 1336 Hz
DTMF 9: 852 Hz and 1477 Hz
DTMF
∗
: 941 Hz and 1209 Hz
DTMF #: 941 Hz and 1477 Hz
DTMF A: 697 Hz and 1633 Hz
DTMF B: 770 Hz and 1633 Hz
DTMF C: 852 Hz and 1633 Hz
DTMF D: 941 Hz and 1633 Hz