Stlrs83,
Welcome to the wonderful world of Inter-Tel, uuuuh I mean Mitel. This problem has been around for years and about the time Axxess 4.0 came out they started adding timers to adjust the Rhetorex boards that they were using at the time. I assume they still use something similar since the values have not changed since then and the same information we got then is in the help files today; I just checked lol.
Anyway, Dwayneg has sent you in the right direction, but adjusting the timer he told you will most likely not work properly, but it is worth a shot. I have read many of posts and he is a good technician so I assume he just hasn't run into this problem a lot on the Inter-Tel or 5000 line of products.
Here are my notes on the subject:
We have a new area in Axxessory Talk Miscellaneous Information dedicated to DTMF recognition:
Rhetorex (the manufacturer of the VPC) has developed a more flexible method of adjusting the DTMF sensitivity. Prior to v4.0, we had 2 timers, DTMF Detection and DTMF Delay. Now we have this section dedicated for DTMF detection. The following describes the functionality of these new adjustments:
In most installations, the DTMF detection information should not need to be changed. However, if the IVX500 is missing digits or if DTMF detection is causing talk-off or playoff, it may be necessary to adjust the DTMF filter parameters.
If digits are not being detected properly there three possible reasons:
(1) - The twist is not within the allowed range:
The Twist parameters specify the maximum acceptable difference between the high frequency energy and the low frequency energy. Twist problems are caused mainly by the telephone system. 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.
(2) - 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 parameters should be increased and Ratio parameters should be decreased so that digits can be detected even when stronger noise and other signals exist.
(3) - 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 problem. 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 value of the timers are reduced, DTMF detection is improved, but the possibility 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. 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.
When digits are missed both in Play and Idle modes, the most probable cause is a faulty telephone system. If the duration of the digits and the intervals between them are 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. Once 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.
When digits are missed only in Play mode, the Twist parameters should be increased and Ratio parameters should be decreased for Play mode only.
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: If the DTMF parameters are changed, the new value will not take effect until the Axxessory talk is completely idle.
The definitions of the parameters are:
DTMF Digit Detect On:
This determines the minimum duration of DTMF tones that can be recognized by Axxessory talk during Play Mode (for example, when Axxessory talk is waiting for input). Valid settings for this parameter are 32, 48, 64, 80, or 96 milliseconds. The default is 48 milliseconds.
DTMF Digit Detect Off:
This determines the minimum silence allowed between DTMF tones that can be recognized by Axxessory talk during Play Mode. Valid settings for this parameter are 32 or 48 milliseconds.
The default is 48 milliseconds.
DTMF Digit Delay On:
This determines the minimum duration of DTMF tones that can be recognized by Axxessory talk during Idle Mode (for example, when a prompt or message is playing). Valid settings for this parameter are 32, 48, 64, 80, or 96 milliseconds. The default is 32 milliseconds.
DTMF Digit Delay Off:
This determines the minimum silence allowed between DTMF tones that can be recognized by Axxessory talk during Idle Mode. Valid settings for this parameter are 32 or 48 milliseconds.
The default is 48 milliseconds.
DTMF Digit Low To High Twist (Play and Idle):
This is the difference between the DTMF digit high frequency and low frequency energy (high minus low). To the allow the Axxessory talk to detect a digit that consists of frequencies, the high frequency energy cannot be stronger than the low frequency energy by more than the setting of this parameter. In Play Mode the default for this parameter is 9.2dB. In Idle Mode the default is 8.2dB. Valid settings for this parameter are: No limit, 6.7dB, 8.2dB, 9.2dB, 10.7dB, 12.7dB, 15.2dB, or 18.2dB.
DTMF Digit High To Low Twist (Play and Idle):
This is the difference between the DTMF digit low frequency and high frequency energy (low minus high). To allow the Axxessory talk to detect a digit that consists of frequencies, the low frequency energy cannot be stronger than the high frequency by more than the setting of this parameter. In Play Mode the default for this parameter is 8.2dB. In Idle Mode the default is 5.2dB. Valid settings for this parameter are: No limit, 4.2dB, 5.2dB, 6.7dB, 8.2dB, 10.2dB, 13.2dB, or 18.2dB.
DTMF Digit In To In Ratio:
This is a digit's energy minus the next digit's energy. In order for the Axxessory talk to detect a digit that consists of frequencies, a digit's energy must be stronger than the next digit's energy by the amount of this parameter setting. The default setting for Play Mode is 2.0dB. The default setting for Idle Mode is 8.0dB. Valid settings for this parameter are 1.0dB, 2.0dB, 3.0dB, 4.0dB, 6.0dB, 8.0dB, 9.0dB or 10.0dB.
DTMF Digit In To Out Ratio:
This is a digit's energy minus the noise energy. In order for the Axxessory talk to detect a digit that consists of frequencies, the digit's energy must be stronger than the noise energy by at least the amount of this parameter setting. The default setting in Play Mode is 1.0dB. In Idle Mode, the default is 4.0dB. Valid settings for this parameter are: 0.5dB, 1.0dB, 2.0dB, 3.0dB, 3.5dB, 4.0dB, 4.5dB, or 5.0dB.
Notes:
Increase twist settings makes digit detection more sensitive
Decrease twist settings makes digit detection less sensitive
It appears to be a matter of adjusting the new machine to match the network of phone lines. That is why the voicemail box is adjustable! It simply needs adjustment to fit the site.
Note: We had a site that was experiencing talk off when external callers were listening to people's mailbox greetings. It turned out the dealer always changes the voicemail volume to -2 so that the voicemail volume is lower and less susceptible to talk off in that area. The person who programmed a system set the volume at +2 by mistake, and this was causing the problem. Changing the volume to 0, or -2 has cleared the talk off. They did not experience any talk off internally.
Maybe swapping the boards will change the voicemail box response enough to make a difference, but I doubt it. The first row of timer adjustments recommended is a normal response to addressing a problem of this nature. It appears the problem can be different than expected.
You can be dealing with many variables with regular phones and cell phones, which includes the quality of the phone lines to the system, to the cell phone service, THE RADIO TRANSMISSION of the cell phone and the quality of the cell phone itself. DTMF is an analog signal and is subject to high frequency and low frequency loss through the transmission medium. Very often there are losses through the phone lines, analog loop start/ground start lines especially!
Set the DTMF parameters TIMERS (top row) back to default (48, 48, 32, 48). Changing the DTMF Delay On timer from 48 msecs to 80 msecs may correct the problem. If you have tried increasing the DTMF 'timers' and it has little or no effect on talk off or playoff, I personally have had a greater success with the following:
To address a frequency response issue, compensating for line quality (usually high frequency roll off), adjust the second row: LOW TO HIGH TWIST and HIGH to LOW TWIST DTMF Parameters. These will affect the voicemail box FREQUENCY RESPONSE to the DTMF tones. Increasing the setting makes the unit more sensitive, compensating for high or low frequency LOSS through the phone lines. I usually recommend increase each item by a maximum of two settings (i.e. 9.2 increases to 10.7 then 12.7 if 1 "notch" does not help.)
The recommended settings to make the AA/VM more sensitive than default would be:
Low to High Play, Low to High Idle, High to Low Play, High to Low Idle
12.7 10.7 13.2 8.2
The recommended settings to make the AA/VM less sensitive than default would be:
Low to High Play, Low to High Idle, High to Low Play, High to Low Idle
8.2 6.7 6.7 4.3
I want to make an awareness on this: A negative effect of increasing sensitivity might be "Playoff" or "Talk off" where the voicemail box will falsely detect a digit on speech. Decreasing one or more of these timers may be required if the voicemail box gets too sensitive.
If you are using Loop Start lines, you may also change the Hybrid Balance in trunk programming.
In addition, bear in mind when you are dealing with a radio device (cell phone), the nature of the beast is THEY CUT OUT especially when in fringe range areas and when in high rise buildings and overpass areas. When they cut out while dialing, the VM cannot distinguish the digits lost or you may get a double digit detected on a single digit. It is recommended when you can tell the cell is cutting out, STOP at a clear transmission location, or use land line if you are nearly out of range. This sort of thing is not the fault of the Inter-Tel equipment.
So, straight from the help files and my own personal notes I bring to you some steps to try and solve the issue.
1. This problem doesn't really show up on digital trunks so I assume you have copper trunks. Make sure that you always run the Loop Loss Test and Hybrid Balance tests on your CO Lines. Have them test to see if that fixed the problem and if it doesn't then go to step 2.
2. Adjust the twist ratios to account for abnormalities in the timing of digits versus frequency response. Remember to keep the ratios the same on these 4 settings as much as possible.
Low to High Play: 12.7
Low to High Idle: 10.7
High to Low Play: 13.2
High to Low Idle: 8.2
Hopefully that works for you on gives you more tools to work with to solve the problem. I would be interested to find out what you had to do to fix this one since I have not run into it in a few years.
Thanks,
TE
