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

[Jon Lawrence]

On Tuesday 12 October 2004 22:58, Rich Adamson wrote:
> Adding resistance to one side of the line only begs for problems
> as it creates a tip-ring imbalance that will "cause" echo, etc,
> when other imperfections exist.
>
> If that approach works at all for anyone, its addressing a symptom
> and not the root cause.
>
> Try this one: Each customer loop is made up of copper and the longer
> the copper, the more resistance. Yet the impedance (in the US) is
> consistently 600 ohms. A short loop might be a 100 ohms while a long
> loop might be well over 1500 ohms; still both are 600 ohm impedance.
>
That's how it should work. The resistance of a loop will change with distance, 
but the impendence of that loop should remain roughly constant regardless of 
distance.

Jon