Media5 Mediatrix 4104, Reference Manual

Page: 261 / 466

DTMF Detection Reference Manual (SIP Version)
Mediatrix 4104 239
DTMF Detection Configuration
Below is a frequency spectrum analysis of a DTMF (9) with the Frequency in Hertz on the x axis and the Power
in dBm on the y axis. The low and high frequencies of the DTMF are in red and you can clearly see that they
are the most powerful frequencies in the signal.
Figure 79: DTMF Detection Example
To detect this DTMF, the DSP relies on several parameters. The following table lists the default values that
the Mediatrix 4104 uses. You can override any one of these values.

To configure the DTMF detection:
1. In the voiceIfMIB , set the maximum absolute power threshold (dBm0) for the low and high
frequencies in a DTMF in the voiceIfDtmfDetectionUnitMaxPowerThreshold variable.
The high AND low DTMF frequencies MUST be lower than this threshold otherwise the DTMF is not
detected.
852 7 8 9 C
941 * 0 # D
Table 153: DTMF Keypad Frequencies (Continued)
Low/High (Hz) 1209 1336 1477 1633
Table 154: DTMF Detection Default Parameters
Parameter Value
MinPowerThreshold -30 dBm0
MaxPowerThreshold 1 dBm0
BreakPowerThreshold 32 dBm0
PositiveTwist 6 dBm0
NegativeTwist 9 dBm0
RiseTimeCriteria confirmSnr