R2511-HP MSR Router Series Voice Configuration Guide(V5)

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Configuring DTMF
Introduction to DTMF
Dual tone multi-frequency (DTMF) uses a mixture of a high frequency tone and a lower frequency tone to
represent a key on a keypad. Each column of keys is represented by a high frequency tone and each row
of keys is represented by a low frequency tone. For example, as shown in Figure 13, the di
git 1 is
represented by the combination of a pure 697 Hz signal and a pure 1209 Hz signal. Such DTMF signals
have good immunity to interference.
Figure 13 DTMF keypad frequencies
A DTMF signal must last at least 45 milliseconds. A minimum interval of 23 milliseconds is required
between two DTMF signals to make sure that DTMF signals are recognizable. Such requirements are
roughly the same in all countries. For more information, refer to the ITU-T Recommendation Q.24.
Configuring DTMF properties
Step Command Remarks
1. Enter system view.
system-view N/A
2. Enter voice view.
voice-setup N/A
3. Configure the duration of
DTMF tones and the interval
between successive DTMF
tones.
dtmf time {interval | persist }
milliseconds
Optional.
By default, 120 milliseconds for
both.
4. Configure a DTMF signal
amplitude.
dtmf amplitude value
Optional.
The default is –9.0 dBm.
4
1 2 3 A
B65
7 8 9
*
0 #
C
D
1209Hz 1336Hz 1477Hz 1633Hz
697Hz
770Hz
852Hz
941Hz
Column Frequency Group