SPA8800 Echo

[fioreit]

Just installed 3cx in our small office a couple weeks ago. 14 users, using Polycom IP 650 handsets. We have an Cisco SPA8800 setup with 4 incoming Analog lines. We've had issues since it started with intermittent echo. The echo is on our end, you can hear your voice echoing back at you.

The worst part is the inconsistency of it. Every test call I make sounds fine, but the users in the office are still complaining that it's happening. They say it doesn't matter if it's an Inbound or Outbound call or if they're calling a Cell # or Landline. It can happen anytime.

I have the Echo Cancellation turned on, I tried turning it off which only made it happen on every call.

Setting the SPA To PSTN Gain: to -3 did seem to help a little.
I have the PSTN To SPA Gain: bumped up to 4 because the line is so quiet otherwise its hard to hear the other party.

Any other ideas besides switching to a Patton VoIP Gateway?

 

[lneblett]

You can try to lower the gain more (if possible) on the SPA to PSTN side. You will know when you reach the limit as users on the other end will complain that they can no longer hear you. You may also need to ensure that the termination is set correctly for the country. Have you also confirmed that the line does not exhibit the issue when using an analog phone hooked directly?

The issue is usually associated to line energy being reflected back to the user due to line impedence issues or simply too much gain. It is a question of having the correct impedence set and then adjusting the gain to minimize the echo. Complete elimination may not be possible as some echo could be originated from the other end, such as if the remote side is on a speaker phone and the mic is picking up the conversation and essentially relaying it back (acoustic echo).

Switching from one brand to another may or may not provide relief as manufactuers oftentimes use the same chip sets and reference designs. You may also want to ensure that the SPA has the latest firmware as perhaps there were some modifications made that might also address how it handles the issue.

 

[fioreit]

Ok so how do I set the Termination for the USA? We're in Wisconsin.

I have the Analog lines coming out of the 66 Block terminating to a RJ45 Patch Panel, From there I have an RJ45 wired with a single pair going to an RJ11 into the SPA.

If the polarity is wrong would that cause echo on a line?

Also what should the impedence be set to?

 

[lneblett]

International Control section (SPA8800)
FXO Port
Impedance
Desired impedance of the FXO Port. Choose from {600,
900, 370+620, 270+750||150nF, 220+820||120nF, 370
+ 620 || 310nf, 320 + 1050 || 230nf, 370 + 820 || 110 nf,
275 + 780 || 115nf, 120 + 820 || 110nf, 350 + 1000 ||
210nf, 0 + 900 || 130nf}
The default is 600.
The impedance values for various countries follows:
US—600
EU (UK, Germany, Netherlands, Sweden, Norway, Italy,
Spain, Portugal, Poland, and Denmark)—270+750||150nF
France—270+750||150nF
Australia—220+820||120nF
New Zealand—370+620||310nF

In answer to your question about polarity, no. However you should check and ensure that it is correct for both FXO and FXS. You can usually find a relative cheap tester at Home Depot. Most modern devices really don't care about polarity anylonger, but I find it good practice to still make sure it is correct. I am uncertain why you are using a RJ 45 patch panel as it seems to be overkill and another potential point for failure. I would normally use the 66 block with bridging clips (if needed) and then use the subscriber (CPE) side to go directly to the Gateway with RJ 11. I can always move the RJ 11 around to whichever port I need on the SPA just as easily as you can with the RJ 45 or with the RJ 11, but I don't have the additional punchdowns on the back of the patch panelor the additional crimping on the RJ 45 to contend with.

 

[leejor]

Confirm too, that it is an issue with all lines and not just one in particular. It could turn out to be a faulty linecard at the central office, or bad cable pair (extra tap somewhere). When you do test calls, be sure they are not just going out on the first line, which may be OK.