B&K 4070A - Manual (Page 32)

BK Precision 4070A User Manual Rev.2.2
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5.16 DTMF Generation Mode
Introduction
Dual Tone Multi Frequency generation mode generates the Touch-tone dialing tones according ANSI T1.401-1988
Section 7.2 standard. The user can specify dialing digits “0” to “9” alone with ext ra DTMF codes “A” thru “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 RS-232 port, the 4070A can be used as a speed dialer; these digits are queued and dialed with the specified
duration and delay between digits.
NOTE: The 4070A 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
DTMF Generation Mode Parameters
The DTMF Generation mode has the following front panel display:
Figure 5.16-1: DTMF Generation mode display
1. Generated DTMF Digit
The last DTMF digit that was generated is displayed in this field. To generate a DTMF digit, the cursor must be
either in this field or the OFF position. If the cursor is in any other field (i.e. Delay or Duration fields) then the
keypad functions to enter those parameters.
DTMF generation: # Duration: 200 mS
Delay: 0 mS Level: -10.0 dBm
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