[Asterisk-Users] Huge Echo

[Marek Zachara]

> > AFAIR, the impedance is not a simple factor, but a combination of passive
> > resistance plus reactance - which usually varies within measured
> > frequency range. Therefore channging the device resistance WILL change
> > its impedance. I know the result will not be perfect, but at least i hope
> > for better load match than it is now. I assume the specified impedance is
> > required within PSTN frequencies which will be roughly 100-4khz, right?
>
> That's not exactly true if you think about it. Since pstn lines are
> typically copper based and have a varying resistance based on the length
> and guage of copper, the copper resistance will vary from almost zero
> (close to CO) to values over 1000 ohms. That certainly does _not_ change
> the AC impedance of the line (regardless of its length); its still 600
> ohms.
>
> I don't recall for sure, but I'm fairly certain the impedance is relative
> to 1,000 hz tone.
>
Yes, I get your point - however from the FXO point of view, the resistance 
will be copper + the exchange port resistance. But this may not have a 
significant impact. Well this means the transformer is the only idea 'left on 
the table' for me now ;)

Marek