Can't fix SPA3102 echo - anybody know of a better box?

Discussion in '3CX Phone System - General' started by PeterR, Sep 28, 2007.

  1. PeterR

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    Hi
    I am in the UK and have been trying for the last week to set up a Linksys SPA-3102 purely to connect 3CX to a PSTN line. I have tried all of the combinations of in and out level and every impedence and echo cancellation setting available but cannot find a setting that enables calls without significant echo. If I adjust the SPA-PSTN and PSTN-SPA levels to make the echo tolerable then the speech levels are just too low. I think I have tried all of the setups available on this and oher forums and have come to the conclusion that maybe the echo cancellation in the 3102 just isn't up to it.

    I wondered if anybody has experienced echo problems with a 3102 which have been fixed by replacing it with another box and if so which one? I would like to ultimately connect to 3 PSTN lines so a 2 or 4-way FXO gateway would be OK but I am nervous about spending a lot more money to have all the same problems.

    Also I would love to hear if anybody in the UK has actually got a 3102 working OK without echo.

    Thanks
    Peter
     
  2. dyntech

    dyntech New Member

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    I have been pulling my hair out trying to get rid of the echo on a SPA-3102 here in the U.S. I have not gotten to the point yet of trying another box. It is now at a level that is somewhat tolerable but, the audio is a little lower than I would like it.

    I also noticed it seems worse on my Cisco 7960 IP phone than it does on the Uniden analog phone that is also plugged into it.

    I read somewhere on another forum that the impedance and audio levels have something to do with how close you are to a central office. I'm pretty close, don't know if it's true or not.

    I got the idea tonight to try adding another DSL filter onto the line since my DSL is on the same circuit, but haven't gotten enough energy together to fight it just yet.
     
  3. PeterR

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    Thanks both for your comments.
    VOIP calls work very well and I do use VOIP for outgoing calls. Currently using Sipgate. There is a bit of a delay but of course no hint of echo and good audio quality. Problem is I work from home and I am trying to get my existing PSTN incoming line into the system

    I am not using the Line 1 FXS port on the 3102 at all - just a Linksys SPA942 IP phone via 3CX. I did try an analogue phone on the Line 1 port but the results were no different. Maybe I will have more of a play with that to try and undertand the problem better.

    The comment about the distance from the local exchange is interesting and may account for why some people have problems and some don't. I am a fair distance - about 4 miles I think, but presumably there are many people who are a lot further than that.

    Does anybody know where the echo actually comes from? I assume that it is caused initially by latency in the 3102, but is my voice being bounced back from the local exchange or is it echoed back accoustically from the remote party. I ask because it does seem to be worse with some calls than others.

    I also have DSL on the same line and changing the DSL filter made no difference (except that I then needed to change the DTMF level to make it dial out) I did try it on another circuit (without DSL) as well but the echo was the same.
     
  4. aznxbandit

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    Peter,

    You need to find somewhere in your gateway configuration, the settings to adjust RX and TX gain to and from PSTN. The settings usually range from -12 to 12. Start with 0 0 and go from there.

    -Allan-
     
  5. PeterR

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    Thanks Allan but unfortunately I have already been that route. The problem is that if I adjust the gain settings so that the echo is manageble, the voice levels are just too low to be usable.

    Peter
     
  6. Anonymous

    Anonymous Guest

    Have you tried the volume on the phone?
     
  7. aznxbandit

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    Peter,

    I see where you're at. My TX and RX gain values are set to 3 and -2 respectively. It works well on Grandstream GPX 2000 IP phones but when I used the new Polycom IP 4000, the sound quality is very poor. Lots of clipping noise and un-acceptable voice quality. I am in the process of ordering analog lines from another PSTN and see if it has something to do with the quality of the POTS PBX.

    -Allan-
     
  8. pishkom

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    Hi guys I am new to 3cx and its forums but I think my 2 cents might be able to answer some of yalls questions and also give you ideas for trouble shooting this issue.

    First question is if we knew of a better box and I have to say that I have had great success with Grandstream devices such as their old school HT488 as well as one of their new HT503. When you get ready to get a 4 port gateway or more and you are on a tight budget the Grandstream gxw4104 and 4108 are a perfect solution for this.

    Having said this I can explain to you where this echo is coming from and also why sometimes your calls are probably mixed with a bit of static.

    All of the FXO ports have a LEC on them which is very sensitive to overdriven TX signal from a IP phone. And to be exact the IP phone that you are using is a perfect example of bad TX handling. The SPA942 that I have here with the lates fw 5.1.15(a) drives the audio beyond the codec limitation this creates clipping and therefore harmonic distortion which is the biggest enemy of a LEC. So when audio gets to the LEC on the SPA3102 FXO port it cannot be used to update the current LEC model so it is just passed through to the 4-2 wire transformer bridge. Here is where the AC impedance plays a row and it could either decrease or increase your ERL (Echo return Loss) but regardless of the AC termination and gains of the FXO port if the audio is overdriven the LEC will not even try to process the incoming audio from the PSTN(this would be the incoming signal plus the echo bounce) and will just pass it through and “you hear echo” or try to clean up the echo based on a previous estimation in which case you hear “static noise“.

    This was just on overview of LEC implementation, I really don’t know what method of LEC is Linksys (Sipura) using in their device but I know for a fact that I have never has this problem with Grandstream devices. I was using their gxp2000 phones with a gxw4108 and after Grandstream released their fw 1.0.4.22 for their ip phones all the echo problems were solved
     
  9. dyntech

    dyntech New Member

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    Peter,
    I added a second DSL filter and it did not good at all. I seem to get the same "lack of quality" whether I use my Cisco 7960 or my Uniden analog phone.

    I have adjust the gain controls as well and am at the same point you are, the audio is somewhat acceptable but the volume is way too low. My VOIP calls however sound great.

    Maybe Linksys will update the firmware soon and fix this.
     
  10. RobLloyd

    RobLloyd Member

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    I've given up on linksys devices except for the phones. Their support doesn't help any and they aren't to quick to resolve any issues.

    I'm trying a Grandstream GXW4104 with good luck so far. If I run into issues I'll try the AudioCodes and then Patton.
     
  11. dyntech

    dyntech New Member

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    FYI,
    Audiocodes is no better than Linksys except that they cost a whole lot more.

    The best gateways I have found have been Mediatrix. But, 3CX does not support them.
     
  12. RobLloyd

    RobLloyd Member

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    I guess everyone's mileage varies with devices. I've heard great things about AudioCode's gateways. Maybe it all depends on your PSTN line quality, network hardware, etc.

    Maybe there is no perfect one!???
     
  13. erich_richker

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    I had problem with echo before I unbound the device from the media server problem solved.
     
  14. iang

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    I'll throw in my 2 pence / cents worth only because I've got a Linksys SPA921, SPA3102 and I'm in the UK :)

    Configuring the SPA3102 was a complete nightmare. I did have some echo initially but I didn't worry about it because I couldn't make outgoing calls to my PSTN line.

    After upgrading the firmware on the phone and gateway and setting all the regional tones, FXO settings, etc for the UK when I came to look at the echo cancellation problem, it had disappeared!

    PeterR, if you're still monitoring this thread and struggling with the SPA-3102 I'll happily share my config with you to see if it helps.
     
  15. regisit

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    Hi all, I too have a 3102 (in the UK) and basically cannot use it. Not because of echo, but because the sound level is so low that nobody I call can hear me. A piece of string and two tins would be better! I too have gone through all the various 3102 settings I can find but nothing seems to fix it. It doesn't matter what device I use to make the call: SNOM 370 IP phone, softphone or an analog phone attached to the 3102. The only thing that fixes it is switching the thing off, but that rather defeats the object!

    Anyone got one to work at least acceptably in the UK and would care to share their config for all here?

    Many thanks,
    Adam, Regis IT Ltd.
     
  16. Henk

    Henk Member

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    With echo it depends what side of the device it happens, generally it can be fixed with

    PSTN To SPA Gain field, enter lower values. This will reduce the sound on your side, this might result that you hear the caller not as good, but it can reduce the echo.
    Select from the list box in FXS Port Impedance field Select another value. This works better on ADSL connections than it is on CABLE. Also check the ADSL filters.
     
  17. Henk

    Henk Member

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    Re volume on phone


    FXS Port Input Gain and FXS Port Output Gain, enter higher values (make sure to do it in multiple of 3s)
     

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