We treat problems with dialing a GPON router from MGTS

GPON walks around Moscow. Related problems are spreading. In this article, I want to share my experience in treating the incompatibility of the MGTS router with an existing telephone, which manifests itself in random errors when dialing a number.

Lyrics
Once upon a time (2-3 years ago, it seems) I wanted to make myself a backup Internet provider. And I began to look towards the daily ADSL tariffs ( archive ) from MGTS. It was then that I came across a new word for myself “GPON”, and also realized that it was too late to install ADSL - soon they would optics anyway. Then, after viewing the profile topics, I had the first negative impression of the reliability and reasonableness of this design.

The first live GPON I saw with my elderly relatives. Of all the functionality offered by MGTS, they are only interested in regular telephone communications, the reliability of which, they said, has fallen significantly. And this week, GPON came to me.
Forget about:
  1. Why is MGTS needed?
  2. How security issues are allowed, such as the same WPS PINs
  3. What else can you squeeze out of the router (otherwise you can sit for a long time)
  4. About wonderful people who came up with a “default” password from a WiFi phone number.
  5. What are the ugly blunt cleavers for the installers (if anything, the cleaver is a device for obtaining a clean and even surface before welding).
  6. As half of the process goes on weight (and the second half on the knee).
  7. As they don’t even know the “chips” like “wet breathing” on the cleaver (so that the gum holding the fiber holds a little better).
  8. Why are they stupidly blankly watching how welding is trying to create a small miracle by welding a uniquely bad chip with more or less decent (although if you stop welding, it would be enough to redo only one chip).
  9. Why they don’t have a refractometer or even a power meter



First bell


In the presence of the installers, I only managed to verify that the dialing on my Philips SE 2752 became unstable - I got one out of 3 calls to my mobile phone. Moreover, the effect was approximately the same both in pulsed and in tone mode. From the installer, I learned that I was not the only one with similar problems (which, in fact, prompted me to write this opus). Nevertheless, an old noname tube was removed from the mezzanine, on which dial-up in a pulsed mode was normal (and similar bugs were observed in tone mode). On which we said goodbye.

Opinion about "SE 2752" for a couple of years of use I have developed is by no means high. In 2 out of 4 handsets, the displays died within two years (and the problem is not in the displays, but in the contacts - the displays just lie pressed to the contacts). Therefore, Philips was appointed extreme.

What to check


Unfortunately, I did not find such a list, so I’ll try to make it myself. So, in order not to tear your hair afterwards, it is advisable to check:
  1. The power of the incoming optical signal is
    checked through the web interface of the router "Home> Device Info> GPON", from under the service account , from under "admin-admin" this page is not visible (correctly, why do people upset again). I just, right after welding, asked the installer to show the result.
    Must be at least -29 dBm. [ Amendment ]. In my case (after 7 attempts) “the first time” it turned out -15.23 dBm, which, as I understand it, is normal, it makes no sense to redo it. However, do not trust the installers, if they assure you that -50 dBm is also normal , it is better to immediately ask "try again".
    screenshot


  2. The operation of the phone
    Everything seems to be clear here. Make a call-receive a call. It is desirable several times.
  3. WiFi
    Password The default password was written on a sticker inside the box. For some reason, the installers changed it to% phone number%.
  4. SSID WiFi
    In our entrance, it seems that half were changed from the default "MGTS_GPON _ ####" where #### is a random number, to "MGTS_ ###", where ### is the apartment number, and half were forgotten.


First steps


  1. Save the initial settings.
    It is impossible to do this from admin, but otherwise everything is simple. Just go to "Home> Management> Config File" and click "Backup".
    screenshot


  2. WiFi settings
    Change the password ("Home> Configure> Wireless> Security")
    Change the SSID (name) of the WiFi network ("Home> Configure> Wireless> Basic")
    Turn off WPS ("Home> Configure> Wireless> Wi-Fi Protected Setup") , just in case
  3. Disable WiFi ("Home> Configure> Wireless> Basic") if you still do not plan to use it - why take up an already tight 2.4GHz broadcast?)
  4. Do I need to change passwords?
    You can change the password from admin and even in some sense need it. However, this does not give much, because The password for the MGTS account with wider privileges is still widely known, and you probably should not change it . According to the installer MGTS from time to time updates the firmware . Of course, the new firmware can either bring something useful (for example, new network settings, without which nothing will work), or break something useful. So everyone is free to decide for themselves.
    The seriousness of MGTS’s intentions in terms of remote access to the router is evidenced by the fact that on the page "Home> Management> Access Control> User Management" there is no way to deny access from WAN:



    Although the «more info» it is mentioned:

    .
  5. Check what kind of agreement you “concluded” with MGTS.
    For example, I did not fill out a piece of paper on the provision of two-month free “trial” access to the Internet, but it still works ... Moreover, it happens, it seems, also like this , ( for the archive ).


Device


So, we made the first settings. Now you can in a relaxed atmosphere, a little closer look at what we got:
.
Not difficult:
  1. To google MGTS "instruction" (for archive ).
  2. Find some technical notes ( for the archive ).
  3. And also understand that, probably, with a certain amount of time spent, you can squeeze almost anything from the router .

... and I think that's it. I did not find anything else (maybe I was looking badly, of course), neither alternative firmware, nor detailed instructions ... Including in the plane of solving problems with dialing.

Dianostics: the story of one debug


(To whom it will be uninteresting - go to the chapter "treatment")

Let’s try to understand what exactly is going wrong. For the same purpose, it is very logical to use the "call log" ("Home> Management> LOG> Call Logs").


However, I was pleasantly surprised by the opportunity to approach the issue more carefully using the built-in diagnostic utility ("Home> Management> Diagnose> Voice Diagnostics> Telephony Diagnosis"):


The first 4 steps are elementary,
If anyone is interested in screenshots





But with the 5th step - this is what we are looking for.

  1. Click "Start step 5",
  2. wait for the router to be ready
  3. pick up the phone
  4. dial any number
  5. waiting for short beeps
  6. hang up
  7. wait until the page is updated
  8. we compare what we wanted with the reality with what we typed with what our Chinese friend “heard”

For example, in this case I dialed “123456789”, and everything turned out fine:

... and in this: “12345678901234567890”, and again everything is fine:


Trying “998877665544332211”


- a mistake, the first 3 digits are missing somewhere

Trying “999888777666555444333222”


- again a mistake, the first 2 digits disappeared, and the 3rd “9” was replaced by “8”.

After a dozen attempts, it becomes clear that if the first digits are 8 or 9 - they are likely to be lost. If 1 or 2 - no problem. In isolated cases, “9” is replaced by “8”.
By the way, pay attention to the typo of “nmber” - it seems to subtly hint at the degree of readiness, reasonableness and accuracy of the product.
So what can we change?
The list of available settings is essentially limited to the page “Home> Service> Voice> Phone”


More info .
In Russian, as you can see , it’s never understood.Moreover, in my opinion, the Russian “more info” is even more misleading in terms of gain parameters (details below ).

Timings


Timings were the first under my suspicion. There are already two such settings. Min-Hook-Flash and Max-Hook-Flash. My ear told me that 450ms was more than enough for “the maximum playing time of one tone,” but 80ms, how the minimum time can raise questions. Therefore, I was very disappointed when I found out that this parameter is not set to less than 80 - it is reset to the previous value after clicking Save. The maximum value in this case is “Max-Hook-Flash”. At “Max-Hook-Flash”, the minimum value is obviously equal to Min-Hook-Flash, and the maximum is 2000. It is not difficult to
find any specifications of the DTMF standard (but how much they relate to this case, of course, is another question).
If the dear reader does not know the DTMF device at least to the extent that itdescribed in the Russian-language Wikipedia (as I did not know it, until today for, and I) - I highly recommend reading it. Useful s. Otherwise, it will not be clear further.
About the duration of the pulses, you can find, for example, the following words:
* The values ​​shown are those stated by AT&T in Compatibility Bulletin 105. For compatibility with ANSI T1.401-1988, the minimum inter-digit interval shall shall be 45msec, the minimum pulse duration shall be 50msec, and the minimum duty cycle for ANSI- compliance shall be 100msec.

And I even more firmly established in my assumption - it turns out somewhere at least as much as 50ms it is considered where to pick up with a minimum of 80ms ...
Well, if they don’t give it down, let's at least turn it up. At least we will be convinced that this is precisely the case. We are trying to set both parameters in 2000 - if it is not typed at all, then at least these are the parameters that we need. But it was not there. Even with these settings, the result is the same - all the same numbers are lost. The situation is absolutely the same. Yes, of course, I clicked Apply, and rebooted the router and then double-checked again - it did not help. It reboots, by the way, this is a Chinese miracle for so long that you begin to suspect that the bobik is dead - I could only get into the admin panel after 10-15 minutes.
Then I also tried with settings 300-500.
Just in case, I tried both in the "Diagnose" mode and in the "combat" dialing mode with subsequent verification by the log. I didn’t notice the difference.
Thus, there is a strong suspicion that these settings, unfortunately, do not work at all. [ Amendment ]

Measurements


Just in case, I decided to check my assumption and measure the pulse duration. Of course, it would be possible to take a normal oscilloscope, but suddenly I became too lazy to mess with the wiring, I wanted to solve the problem with less blood. Based on the fact that when dialing a “with the handset” dialing, it emits all the same sounds that go in line, I just recorded them on the WAV Recorder of my N7100 (popularly Samsung Galaxy Note II). I wrote down two “combinations”: “ rec1 ” and “ rec2 ”.
Further, for each of the combinations, using Matlab R2014a, two spectrograms were constructed:
To estimate the tone frequencies: with a time resolution of 10ms, and a frequency resolution of 20Hz:
            Fs = 41000;              % Sampling frequency
            window = 0.01/(1/Fs);    % Time resolution is 0.01 second
            noverlap = 0;            % No "smoothing"
            nfft = 0:20:2000;        % Frequencies
            spectrogram(data,window,noverlap, nfft,Fs);
            


(Try to guess what combination this is :))
hint
  1. Up to 3rd second, the handset is not picked up
  2. Up to the 5th second there is a dial tone inviting to dial the number
  3. Up to ~ 9th second, dialing continues
  4. Until ~ 13th second there is silence in the handset - the router ponders what he heard
  5. Up to ~ 16th second short beeps in the handset - invitation to hang up


(and this? )
To estimate the duration of a tone: with a slightly better time resolution: 5ms, and a frequency resolution of 50Hz:
                Fs = 41000;              % Sampling frequency
                window = 0.005/(1/Fs);   % Time resolution is 0.005 second
                noverlap = 0;            % No "smoothing"
                nfft = 0:50:2000;        % Frequencies
                spectrogram(data,window,noverlap, nfft,Fs);
                


Result:


Even larger:


So, it is easy to see that the pulse duration is 100ms (± 20ms), which, of course, is close to the allowed limit (80ms), but does not violate it. The gap between the numbers also looks normal, the same ~ 100ms.
Of course, all sorts of bad transients in a lousy network and with a lousy amplifier can ruin everything, but what can you do ...
And yet, what else do we have left in stock there?
ABOUT! Amplifier!

Treatment


We take and change the gain, for example, put everywhere 6dB
  • Transmit Gain = 6dB - hardware gain of the signal going to the phone (as far as I can judge on the basis of the English “more info”)
  • Receive Gain = 6dB - hardware gain of the signal coming from the phone
  • Speaking Volume = 6dB - software amplification of the signal coming from the router via VOIP
  • Listening Volume = 6dB — программное усиление сигнала, приходящего в роутер по VOIP

Thus, as already mentioned above , in my opinion, the Russian-language “more info” is more likely to be misleading than to provide useful information. (Therefore, the screenshots are everywhere and the English interface, despite the fact that the Russian language seems to be).



As a result, even more numbers are cut off, and from “998877665544332211” only “332211” remains. And



... oddly enough: when dialing 112233445566778899 everything works:



Well, as they say, a negative result is also a result, and this is even more so.
We try the zero parameters:



And we get:



- Hurray! Earned!
(I also checked “0”, “*” and “#” - they also work as they should)
Now, with a clear conscience, we can also get this picture:


Well ... what domestic product does not need to be finalized with a file?

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