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.
