Dtmf Detection Information - Inter-Tel AXXESS Manual

Programming
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INTER-TEL AXXESS
B. DTMF DETECTION INFORMATION
NOTE:
12.4 In most installations, the DTMF detection information should not need to be changed.
However, if the Voice Processor is losing digits or if DTMF detection is causing talk-off, it
may be necessary to adjust the DTMF filter parameters.
12.5 If digits are not being detected properly, there are three possible reasons:
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•
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12.6 There are six DTMF filter parameters that can be adjusted to improve performance
when the DTMF detection is not performing as desired. These six filter parameters have one
set of values when a recording is being played (Play Mode) and another set during all other
functions (Idle Mode). Thus, there are twelve parameters used to control digit detection.
12.7 When digits are lost both in Play and Idle modes, the duration of the digits and the
intervals between them may be too close to the DTMF Delay and DTMF Detection values.
You should decrease these values to improve the chances that the digit's characteristics will
remain within acceptable values during the minimum required duration. After the minimum on
and off times are set according to the pattern of the digits being dialed, the next step is to verify
the twist. A spectrum analyzer can show the amplitude for the frequencies in the signal, and
the values shown can be compared to the twist limits set in the driver. Rhetorex has a utility
called "FFT" that will show the basic characteristics of the signal, including frequencies and
amplitudes. Increasing the twist parameters for both Play and Idle modes will usually solve the
problem.
12.8 When digits are lost only in Play mode, the Twist parameters should be increased and
Ratio parameters should be decreased for Play mode only.
12.9 If talk-off is occurring, increasing the minimum duration of the digits should suffice. If
this is not possible due to other constraints (e.g., speed dial), Twist and Ratio parameters
should be changed to make the filters less tolerant.
NOTE:
Processor is completely idle.
Page 6-428
MANUAL VERSION 11.0 – May 2008
The DTMF Detection Information field is not supported in Enterprise Messaging.
The "twist" is not within the allowed range. The Twist parameters specify the maxi-
mum acceptable difference between the high frequency energy and the low frequency
energy. One frequency can be much stronger than the other, or the frequencies can be
off the nominal values. If the frequencies are off, measurements made at the nominal
values can show different readings since the peak will be at a different frequency. In
some cases, noise or voice on the line can add to or subtract from these frequencies.
There is too much noise. Noisy lines can introduce distortion to the digits. A simple
inspection can identify if the lines have too much noise. If this is the case, Twist param-
eters should be increased and Ratio parameters should be decreased so that digits can be
detected even when stronger noise and other signals exist.
Another signal is present that is similar to the DTMF digit. Other signals present on
the line, including some types of voice, can be detected as DTMF tones causing "talk-
off." Adjusting the DTMF Detect and DTMF Delay parameters may correct this prob-
lem. However, changing the DTMF Digit Delay or DTMF Digit Detection timer values
is a trade-off between improving DTMF detection and increasing the possibility of talk
off. As the values of the timers are reduced, DTMF detection is improved, but the possi-
bility of talk off increases. As the value is increased, the possibility of talk off is
reduced, but the possibility of DTMF detection problems is increased.
If the DTMF parameters are changed, the new value will not take effect until the Voice

DTMF Detection Information