[Asterisk-Users] Chaining more than one zap echo canceller?

[Kris Boutilier]

You're refering to inserting artificial resistance on just the tip -
wouldn't that introduce a longitudinal imbalance between tip & ring? 

> -----Original Message-----
> From: Chad Scott [mailto:chad at idworld.net]
> Sent: October 12, 2004 11:33 AM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] Chaining more than one zap echo 
> canceller?
> 
> 
> If you're certain it is an impedance problem and the 
> impedance of your 
> line is lower than that of the CO, you can increase the impedance of 
> your line by putting a potentiometer in-line and adjusting it 
> until the 
> sidetone disappears.  This is a bare-bones solution and decreases the 
> efficiency of the line because you're putting in pure resistance.
> 
> If your impedance is higher than the CO, or if you want to be more 
> efficient, you'll need a more complicated impedance matching network.
> 
> On Oct 12, 2004, at 10:26 AM, Kris Boutilier wrote:
> 
> >  I have Asterisk connected to a channel bank via a t100p card. There
> > excessive sidetone generated on the analog side due to an impedance 
> > mismatch
> > - I am very close to my serving CO which brings the line 
> down to about
> > 150ohms and the channel bank is expecting 600ohms. However, 
> the very 
> > loud
> > sidetone is being fairly effectively supressed by the zap echo 
> > canceller and
> > I have quite usable lines as a result.
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