"Echo" problems on calls, poor audio

Discussion in '3CX Phone System - General' started by zooeyhall, Mar 10, 2011.

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  1. zooeyhall

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    Hello everyone--I am hoping I can get some general troubleshooting insights on a problem we are having in one of our 3cx phone installations. I'm the IT person for my company, but am not dedicated exclusively to phone systems so I am by no means an expert in the more obscure aspects of phone problems--just to let you know.

    Users at one of our locations are complaing of a prominent "echo" on certain calls. It doesn't seem to affect every call. The "echo" is noticed by both the person calling and also the person receiving the call. The "echo" is continuous during the length of the call. It only occurs on external calls.

    This is a simple installation of 6 phones all connected via the internal LAN. There are no routers or anything between the phones. The phones are all Snom 300 phones. Calls are made via external analog PSTN lines, through a Patton 4114 gateway.

    All phones are running the latest firmware.

    We were using these phones at a previous location with 3cx. We moved this office to a new location, during which time I moved the phones. I also setup a new computer (dedicated) with the latest version of 3cx. I installed a new Patton gateway at the same time.

    I know a lot of things can cause this issue, but I am hoping for some good general recommendations on troubleshooting this issue. I am looking at implementing 3cx at all of my company's locations, so this problem location is sort of a "test" that I am really want to work as well as possible.

    Any advice appreciated. Please post if you need further info.
     
  2. abc123

    abc123 Active Member

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    Re: "Echo" problems on some calls

    Echoes are normally generated in the PSTN. The best place to cancel them is in the Patton. They have an integrated echo canceller and it is adaptive (only works on an echo that exists). It is recommended to switch it on.

    To enable/disable the echo canceller:
    NODE (pf-voip) [default] #[no] echo canceller

    To configure the default profile
    NODE (cfg) #profile voip default

    If it still doesnt clear up then there is probably a problem with the Patton (unlikely) or the lines (most likely). In which case you have to get the Telco in to check them.
     
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  3. zooeyhall

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    Re: "Echo" problems on some calls

    Mark:

    Thanks for the excellent reply. The advice you give certainly makes sense, and I am going to follow up with it on my system.

    I will post back the results, if it worked or not.
     
  4. leejor

    leejor Well-Known Member

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    Re: "Echo" problems on some calls

    Did this just start or has it been a problem from day one? In some cases the echo is a result of the gateway being very close to a central office (or remote), so close that the levels in the gateway need to be attenuated. If levels are too loud even good echo suppressors can be overwhelmed. On an analogue line it would manifest itself as distortion, but, because of the slight, yet noticeable delay introduced by the digital to analogue , and vice versa, conversion, it will result in echo.

    The fact that it is happening in both directions (on all lines, I'm assuming?) would seem to indicate that the echo suppressors are not currently being used and/or some padding needs to be introduced to the circuits.
     
  5. zooeyhall

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    Re: "Echo" problems on some calls

    Hello everyone. I am still having a problem with echo and low volume (incoming audio) in my system.

    I upgraded my Patton to the latest firmware, and made sure that I had Echo Cancelling enabled.

    There was a problem with low volume on outgoing audio. I had to move the output gain to 20 dB, which seems to have helped for that particular problem.

    Users are complaing about low volume/muffled sound on incoming audio---I moved the input gain on the Patton from 0 dB up to 5 dB. However this causes very noticeable echo problems.

    This is a new location my company has just opened. The previous building occupants used a standard PBX. The 3cx PBX setup is very simple: 5 SNOM phones, a Patton 4114, PSTN for outside calls, and everything connected by a LAN with no routers.

    The problem has been present from the beginning (about 3 weeks now). It affects all phones.

    I asked the users about paging and calling between phone extensions. I was told that the echo does not seem to occur in those situations.

    For what it was worth, I hooked up a standard analog phone directly to one of the PSTN outgoing lines and made a few calls. Audio and everything seemed perfect and clear.

    I called the phone company, and they gave me the usual "brush-off".

    There are 3 incoming PSTN lines. One of the lines also carries our DSL internet. I unhooked that line from the Patton, just in case it might be causing the problem, but it made no difference.

    Are problems like this more likely caused by the PSTN lines? Or is it something with the internal LAN? I have done some research, and found articles that talk about "impedance mismatch" and "bridge taps" on the analog side causing the trouble. But unfortunately I am not an expert in advanced telephony troubleshooting.

    I would really like to get this to work reliably. We have 2 locations in our company that are using 3cx, with no apparent problems. I would like to implement 3cx company wide. However the manager at this problem location is "old guard" and was suspicious about this "new fangled" IP phone system from the beginning. If he can find anything to make it look bad to the CEO, he will.
     
  6. leejor

    leejor Well-Known Member

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    Re: "Echo" problems on some calls

    You mentioned originally that the echo was occurring on some calls. Were you ever able to determine any pattern as to which calls had or didn't have a problem. If it were every external call and there were no issues when you connected a set directly to the gateway, then I would have to assume it is something else on your internal network. Do all the sets pass through a switch that is external to your router? If so have you tried swapping that out or bypassing it? What codec are you using? On occasion the condition of the phone line, length, distance from the central office, etc., can affect call quality. It could be the riser pairs in the building you are in. Even a bridged pairs to another part of the building. However, if some calls are clear, and you've determined that the problem happens on all of the lines and not just one or two, then you need to confirm that it is happening on all calls, that would point to an internal, network issue.
     
  7. zooeyhall

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    Leejor: Thanks for the reply. As far as I can tell now from the feedback from people at the location, the echo is present on all calls, some to a greater and some to a lesser extent. There is also an issue with "fuzzy" and low audio volume on calls. I think this generalized distortion is the reason that, when I turn up the volume on the Patton, that the echo increases drastically.

    It's a very simple setup at this location. All phones and the Patton Gateway are connected to a single network switch.

    I was trying to determine the codec I was using. It would be the default one that goes with the installation. Can you advise where I can check this? (as I mentioned, I'm not a thorough expert on using the system yet). It would, however, be the same default I am using at our other installations with no problem.

    "Internal network issues" is a rather broad term--can you perhaps advise some troubleshooting steps to determine if this is the cause.

    As the IT person in a small company, I have to wear alot of hats. I'm not a dedicated telephony expert, and by no means know all the "ins and outs" of advanced troubleshooting in the field. So be sure and tell me any steps I need to take, even the obvious ones! Thanks.
     
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