[Asterisk-Users] Anyone using * in a live production environment?

[Andrew Kohlsmith]

>     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