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Thread: Last ring from fxo going into sip call

  1. #1

    Unhappy Last ring from fxo going into sip call

    Hi, We I answer a call rom the fxo, sometimes I ear the last ring from the fxo resulting in a big buzz. Is there something I can do about that?

    Thanks

    Benoit

  2. #2

    Default

    Do you have any device between the FXO port of Quadro and carrier line? If regular analogue line from carrier is connected to FXO port of Quadro, that situation would not be possible at all because as soon as carrier detects FXO off-hook, is should stop the ring signal and open the voice channel.

  3. #3

    Default

    No, the FXO is plugged directly in the cable modem. I got this problem from 2 differents cable modem in 2 different locations but from the same Quadro 6L.

    Thanks

    Benoit

  4. #4

    Default

    Did you try to test a regular analogue phone connected to that cable modem?

  5. #5

    Default

    Until I configured the Quadro, it was a regular phone and there was no issues. On the second, It was an Asterix with a Digium card without issues.

    Benoit

  6. #6

    Default

    To minimize the load on the CO line Quadro is limiting the off-hook current to 10 mA. This current shall be sufficient (according to standard) for detecting by CO switch the off-hook condition on the line and stopping the ring signal. It seems your modem has difficulties in detecting low current which results in off-hook detection delay. If my assumption is correct then you can increase the current limit on Quadro FXO and resolve the issue. The procedure is as follows:
    1) open the “fxocfg.cgi” hidden page, enable the “custom FXO data” and copy the “FXO csrs”.
    2) paste the copied value into Windows calculator opened in Dec mode and convert it to Hex format.
    3) open another calculator in hex mode and manually enter the Hex value shown in the first calculator changing the first Hex digit to “F”
    4) convert the value in the second calculator to Dec format.
    5) enter the resulting value into “FXO csrs” field on Quadro and save.

    Let me know if it helps.

    thanks,
    hrant

  7. #7

    Default not working

    Hi,

    I did change the values. But it's not working, maybe a little bit but hard to tell. I bought another 6L and did the same thing. The 2 units still having this trouble.

    Can I but more aggressive values?

    Thanks

    Benoit

  8. #8

    Default

    If you strictly followed the procedure described above then the FXO chip on 6L is set to maximum current - 16 mA. You cannot have more with that chip.
    Did you look at the cable modem configuration, maybe there is some off-hook current sensitivity parameter to fine-tune?
    If you can get a milliammeter and do some testing, it could give us more insight into this problem. Just connect the meter into the line between Quadro and cable modem and measure the current when the Quadro extension answers the call. Do the same test with the analogue phone connected to modem instead of Quadro and post both values.

    thanks,
    hrant

  9. #9

    Default

    Hi,

    I did the measurements. On my multimeter, I read 38.4mA, for a call from the Quadro and from a regular phone. The only difference, while the phone is ringing, if I answer the call, the Quadro cannot drain more than 2mA, then after the ring complete, it goes to 38mA.

    The Modem ring indicate 74VAC on my multimeter. If I put a 10KOhm resistor in parallel with the phone line the problem disappear (does not with a 20K). I do not detect difference in the call. I will see next week if it introduce echo but it's purely resistive so I do not think it's a problem. What do you think?

    For your records, the cable modem is an Arris TM722G. The second one is also an Arris but I don't have the exact model.

    Thanks

    Benoit

  10. #10

    Default

    Hi,

    I would like to clarify the setup we are having issue with.

    From the above I understood that we have 6L connected to the cable modem.

    Since 6L has only 6fxo ports and no fxs to hang the phone, where do you hear the ring buzz? On the IP side?
    If yes, then it means that the fxo is already in off-hook state and the call is established.
    But, if fxo went off-hook the cable modem's fxs port should detect fxo's off-hook state and perform ring-trip function (remove the ring signal from the line). Minimum off-hook loop current of fxo port is around 10mA which should be more than enough for any CO or fxs port to detect off-hook state.

    Have you tried to connect the 6L fxo port directly to CO line? Do you still hear same ring noise with CO line?
    This is to understand if we have issue with these exact samples or the cable modem. I'm asking because 6L is used in many countries for years and we never had any issues related to fxo going off-hook and/or CO detecting off-hook state.

    I checked the Arris TM722G and it is not clear what kind of fxs port it has. Does it have any settable parameters? It could be that some mismatching in country specific parameters in modem's fxs and quadro's fxo port is causing this behavior. Quadro allows you to choose the country (meaning telecom standard's requirements) for fxo port that sets the appropriate country specific settings. Can you do the same for modem's fxs port?

    Please answer questions above before we dig farther.

    Thanks

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