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

[Chad Scott]

Impedance is the measure of total opposition (resistance, capacitance, 
and inductance) to alternating current flow.  Adding resistance will 
raise the impedance of the line.

On Oct 12, 2004, at 12:58 PM, Rich Adamson wrote:

> 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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>>
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>
> ---------------End of Original Message-----------------
>
>
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