The GXW-4004 and freepbx echo what to do?

Actually using the GXW-4004 prosrochena 3 lines for analog phones, when calling them with regular ip phones observed echo from the ip phone and from analog, everything is OK, where to dig?
July 2nd 19 at 17:38
2 answers
July 2nd 19 at 17:40
Echo Canceller in the GXW-4004 is included? Jitter buffer?
July 2nd 19 at 17:42
to analyze the rtp may echo appears from behind the curve of the headset or included samoposluga on the client side.

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