ATA 186 / 188 impedance

Unanswered Question
May 30th, 2007


I'm having some problems with a XeroX workcentre Pro in combination with an ATA 186I2-A

I'm suspecting i bought the wrong ATA, but i cannot find which one i need to use.

The :

Cisco ATA 186 with 600 ohm impedance


Or the

Cisco ATA 186 with complex impedance (270 ohm in series with 750 ohm and 150 NF in parallel)


Can anybody tell me which country / region uses which ATA ?

I am now trying to get this to work in Geneva, Switzerland.

The reason why i susspect that the impedance is the problem is that the first port gives an background noice when the fax picks up the line. If i use the same fax same cables etc etc but put it in the second port of the same ATA its realy silent.

Anyway, if this is the problem or not, I do want to know where I need to use which ATA (impedance).

Thank you for your time !

I have this problem too.
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Paolo Bevilacqua Wed, 05/30/2007 - 19:10


On short distances, impedance mismatch is not really a problem. Also consider that chances are, your xerox is not especially manufactured for Swizerland, and just uses the common 600 Ohm.

What is worrying is the background noise on 1st port only, does it happens with any phone / fax you connect ?

cco_heerema Wed, 05/30/2007 - 23:09

Yes the background noice is specific for this port, so my guess is a hardware mallfunction.

Never the less, faxing stays a problem via this ATA.

It's realy unstable, i'm using MCE 4.0 and the SCCP image (V3.1.0) on the ATA.

Sendings and receiving speeds are fluctuating between 4800 kbps and 26000 kbps. I know the ATA supports 14400 and lower but this faxmachine is just not adjustable so it seems.

I tried everything i could find on the internet (audio modes etc etc ) so now i'm thinking of maybe test with H232 Image on the ATA or maybe and FXO port in my 2800 Router just to get this one fax machine to work.

Anybody a good suggestion ? Up to date documentation seems to be rather poor on this subject.

Paolo Bevilacqua Thu, 05/31/2007 - 17:27


the general consensus it that best result for FAX with ATA is using H.323.

If you want to connect the fax directly to the router, you need an FXS card, not FXO.

Hope this helps, please rate post if it does!


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