Specifications

DTMF Detection Reference Manual (MGCP/NCS Version)
Mediatrix 4100
141
Figure 29: DTMF Detection Example
To detect this DTMF, the DSP relies on several parameters. The following table lists the default values that
the Mediatrix 4100 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.
Raising this value increases the sensitivity of the DTMF detection. Raising this value too high may
also cause false detections of DTMFs.
2. Set the minimum absolute power threshold (dBm0) for the low and high frequencies in a DTMF in
the voiceIfDtmfDetectionUnitMinPowerThreshold variable.
The high AND low DTMF frequencies MUST be higher than this threshold otherwise the DTMF is
not detected.
You could, for instance use one of the following settings:
• -15 dBm0: This configuration detects even more false DTMFs in the voice pattern.
• -20 dBm0: This configuration detects more DTMFs in the voice pattern.
• -35 dBm0: his configuration detects less DTMFs in the voice pattern.
Table 103: DTMF Detection Default Parameters
Parameter Value
MinPowerThreshold -30 dBm0
MaxPowerThreshold 1 dBm0
BreakPowerThreshold 32 dBm0
PositiveTwist 6 dBm0
NegativeTwist 9 dBm0
RiseTimeCriteria confirmSnr