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

[Rich Adamson]

Impedance does not equal resistance. Apples and oranges.

------------------------

> 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.
> >
> >  From time to time calls are placed to other PSTN numbers (even 
> > terminating
> > off of the same CO) that are introducing their own far end echo 
> > component on
> > the line and it isn't being supressed at all - thus my outbound callers
> > begin to hear thei          rownvoiceandgetveryfrustrated.Ihaveto
> > assume the
> > second reflection couldn't be supressed by design - the zap echo can 
> > has
> > already locked on to the sidetone echo after all.
> >
> >  So, I have a fix for the sidetone/impedance problem (PRI on order) 
> > however
> > is it possible to insert another can into the system somehow? For 
> > example,
> > if I were to run TDMoE to a second box and access to the t100p/channel 
> > bank
> > through there?
> >
> > Any suggestions welcome (apart from curing the sidetone)  :-)
> >
> > Kris Boutilier
> > Information Systems Coordinator
> > Sunshine Coast Regional District
> >
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