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

Chad Scott chad at idworld.net
Tue Oct 12 13:20:00 MST 2004


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
>>>
>>> _______________________________________________
>>> Asterisk-Users mailing list
>>> Asterisk-Users at lists.digium.com
>>> http://lists.digium.com/mailman/listinfo/asterisk-users
>>> To UNSUBSCRIBE or update options visit:
>>>    http://lists.digium.com/mailman/listinfo/asterisk-users
>>
>> _______________________________________________
>> Asterisk-Users mailing list
>> Asterisk-Users at lists.digium.com
>> http://lists.digium.com/mailman/listinfo/asterisk-users
>> To UNSUBSCRIBE or update options visit:
>>    http://lists.digium.com/mailman/listinfo/asterisk-users
>
> ---------------End of Original Message-----------------
>
>
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users at lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users




More information about the asterisk-users mailing list