OBiTALK Community

I've been experiencing a small problem on inbound calls on my PSTN line for a couple of weeks, but I've only recently been able to test it thoroughly.  On many inbound PSTN calls, but not all, for the first couple of seconds after I answer an incoming call, there is an annoying echo on the line (primarily my voice echoing).  This disappears after a second or two, and then the call is normal, without echo for the remainder of the call.  I've also noticed that when I access the PSTN line directly by using the # key,  then dial a phone number, I sometimes have this same echo for the first digit or two, then remaining digits are dialed without the echo.

This occurs on all of my telephones, both wired and cordless.  I believe this happens on roughly half of the incoming calls.

Any ideas of what is causing this and how to correct it?  Thanks!

Try to power off your OBi device, but have your phone still connected to PHONE port, then, check on both inbound and outbound PSTN calls, any difference on echo?

Thanks, but I've already done that.  When the Obi is powered down, there is no echo on either inbound or outbound calls.

Where is your OBi located? if outside of US, you might need to adjust LINE port AC impedence to match up local PSTN...

How is the echo level?

Note, LINE port has a default channel RX gain at 5 dB, you may bring it down to see if you can make this short echo less audible ... though it might result in lower volume on your handset ...

I'm located in the US.  The echo is pretty irritating, but it is short-lived for each call (only the first few seconds of each call).

I haven't experimented with the Rx gain, but I'll give that a try.

Thanks for your help!

FWIW, I was experiencing this same thing. This was the reason that I got rid of a Cisco SPA-3102 because it is a documented issue for the Cisco and has been on the books for at least 3 years. They don't seem to be supporting the product any more even though they are still selling them. Anyway, I lowered the RX Gain to 3 on the Obi and it seems to have corrected the issue. Be sure you have build 2384 firmware installed in your unit. It is available in this forum.

The more fundamental way is to match the LINE port AC impedance to your PSTN line. Note, there is a setting on LINE port -

Physical Interface -> LINE port -> AC impedance

The default setting 600 oHm is ideally for a regular PSTN line in US. If you are located outside of US, or you are using some PSTN service but not through regular PSTN line, you may try one of 16 impedance settings, and pick one that minimizes echo if you are experiencing any.

Thanks for the suggestions.  I'm still having a slight problem with it.  The Rx gain doesn't appear to make much difference.  However, I changed the LINE Port AC Impedance value to a significantly lower value, and this improved the echo noticeably.  It's still there, but not quite as prominent. 

I'm still tweaking some of the LINE Port settings, but I haven't seen a big improvement, other than with the AC Impedance value.

Thanks again for the suggestions!

Left/Right------I'm in the US and using a standard CenturyLink PSTN line.  I'm not sure why the standard setting of 600 isn't optimum for my installation, but the lower value worked best for me, after extensive testing.

thanks,

Rob

Hi Rob, yes, I expect a matched LINE port AC impedance would significantly reduce the echo.

You may keep the default channel gain setting so that the volume on your handset won't get affected.

Other settings on LINE port might not have much to do with echo ...