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Echo - Weird Behaviour

This is a little long, but I tried to make it as clear as possible.

I have found a strange behaviour in my VoIP network. Look at these two setups:

KS <-> PBX <-> 1750 <-> 5300 <-> PSTN <-> PBX <-> tel

and

tel <-> PBX <-> 1750 <-> 5300 <-> PSTN <-> PBX <-> KS

The "tel" is a common analog telephone set. The KS is a digital telephone set. There's an IP network between the 1750 and the 5300 (not indicated).

Analog connections exist only at:

- the connection between the PBX and the 1750 (FXS port)

- the connection between the analog phone and the PBX

The PBX connection to the PSTN is digital.

In the first case, one of the analog connections is on the KS side (the connection between the PBX and the 1750); the only remote analog connection, from the KS user standpoint, is the one between the analog phone and the PBX

In the second case, both analog connections are remote, from the KS user standpoint: both are near the analog phone.

In the first setup, the KS user has a *lot* of echo when both users talk at the same time. Also, the KS user perceives that the other party's voice clips a lot (the KS user misses many words, not only part of words). When those voice clips occur, echo of the KS user stops occuring. Notice that the analog phone user doesn't miss *anything*.

In the second setup, what a surprise: there's NO echo at all, either for the analog phone user or for the KS user!! And there's no voice clipping when both users talk at the same time.

Does anyone have any idea of what happens?

Thank you very much,

Paulo.

3 REPLIES
Bronze

Re: Echo - Weird Behaviour

Hi Paulo,

i think you have a problem with the DSPs on your Gateway. Try to allocate the DSP until your failure occurs. Look with the "show voice dsp" command which DSP will be allocated. The voice clips should occur always on the same DSP.

Workaround: "clear interface" or "shutdown and no shutdown".

Hope this helps

Mehmet

New Member

Re: Echo - Weird Behaviour

Hi, Mehmet,

just to clarify: when you tell me to look the DSP, do you refer to the 5300? or 1750? And should the "clear interface" be done at the 5300? and does the "shutdown/no shutdown" refer to the Ethernet interface? of which gateway?

Do you think these measures would help on the echo problem too?

Thank you very much,

Paulo.

Bronze

Re: Echo - Weird Behaviour

Hi Paulo,

verify the DSP s on both gateways. Make an shutdown no shutdown on the "voice interfaces".

---Do you think these measures would help on the echo problem too?

I am not sure:)))

regards

mehmet

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