> 5) Attempt to balance the hybrid at the 2-line to 4 line interface.
This is _precisely_ why my rollouts are all strongly recommending using a channel bank instead of the cheap X100P/TDM400P cards -- a lot of work has been put into the hybrid circuitry to dynamically adjust to the line impedance. I've had no serious issues with the X100P/TDM400P in small scale stuff but the echo cancel IMO should be done where it originates -- at the hybrid. Having said that, I do have "echocancel=32" in my zapata.conf for the T100P connected directly to an Adit600 FXS channel bank. I also have an old CAC AB1 with 12FXS and 12FXO ports I am going to deploy shortly to test things like far-end disconnect and other issues. > be the only real solution. Part of the problem arises from the use of > lower impedance telephone wiring nowdays. The typical characteristic > impedance of Cat5 twisted pair is about 100 ohms and many line cards are > optimized for a 600 ohm line. This is made worse if the DC resistance of > the wiring to the CO switch is relatively low. I haven't tried this This is a neat idea; something I have not thought of. However my ideal PSTN termination is digital (PRI) ... something to eliminate the hybrid altogether, at least on my end. :-) For deployments where I am simply providing VOIP to an existing phone system, I am recommending installing a T100P and a digital trunk for the existing KSU; again to eliminate the hybrid mess, or at least push it off to someone else's problem. :-) > 6) Try messing with Tx and Rx gains. Something I have noticed is that on the Adit600 FXS ports, I have had to set its RX attenuation to -7dB!! (TX to -3dB) If my math is correct, that means I am attenuating 85% of my incoming signal! Is this perhaps what you are referring to with the super-low impedance? Thank you for this super technical and informative post. This is what *-users needs... more tech and less running around in circles with the same issues over and over! Regards, Andrew _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users