How do I get the AA to forward a fax call to the ext with fax machine

Unanswered Question
Jun 17th, 2009

My current AA will detect fax signalling and automatically forward the call to the extension that I designate that has a fax machine on it.

How do I do this with my UC520 and CCA 1.9?

Thank You!

Matthew Castrigno

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mcastrigno Thu, 06/18/2009 - 15:15

Thanks Steven.

The first document looks like I may attempt it. Our mail server is extrernal - any problem with this?

Can't the application referenced be configured just to foward the call to the fax machine?

The second doucument recommeds using a seperate DID for the fax - which is exactly what I trying to avoid.

This product (uc520) is for SMALL business. What I am attempting to so has been a standard funciton of key systems for at least 15 years there must be an easy way to do this??

If not please let me talk to the product manager and explain just how baisc this fucntion is.


Matthew Castrigno

mcastrigno Thu, 06/18/2009 - 15:44

On closer review the first document is not even close to my configuration.

I want the AA to detect the fax call coming in from my SIP trunk.

The second document seems talk about a AA script from a thrid party application.

Fax detection is not part of the call manager or message manager?

What am I missing here - this seems very basic.

Matthew Castrigno

Marcos Hernandez Sun, 06/21/2009 - 12:32

Hi Matt,

As you know, Fax detection (or any form of T.37) is not supported over IP trunks. I am currently putting together an application note that will hopefully clarify this, while offering a step by step guide on how to do fax detection. The reason why we had procrastinated, is that after careful review, many people find it inconvenient having to put their callers through the extra detection time. A front end IVR can mitigate this, but it is still annoying to some.



mcastrigno Sun, 06/21/2009 - 14:35

I have been using a setup like this in my office served by a panasonic system for about 10 years - nobody has ever complained about "extra detection time". If fact they are completely unaware as to how long it takes to dectect the fax. All they do is dial the number and hit send. To them it is just like it is a dedicated fax line.

For larger business other solutions are great but this product is for small business and so many are set up this way.

Marcos Hernandez Mon, 06/22/2009 - 05:26

You are talking about an outbound call (I think), whereas I am referring to an inbound call. We too, place the fax call immediately from a fax machine connected to an FXS port.


mcastrigno Mon, 06/22/2009 - 07:21

Sorry if I was not clear Marcos. I am talking about an inbound fax.

I understand Cisco has company specific issues for this not being on the top of the new feature list due to  multiple platforms. But that does not change the fact that many small business can and do benefit from not having the cost of another FAX line and the existing technology in the marketplace has let them do that for many years.

Of all the cisco platforms this feature should be here - and I know Cisco does put features  some on platforms and not others - and I know getting a platform specific change in IOS is up there with asking the Red Sea to part for you in terms of difficulty but that does not mean UC520 evangelists should not try.

Not trying go to give you a hard time here Marcos, after all you have been very helpful to which I am extremely grateful just trying to make a point that this is a needed and very meaningful feature.

Thanks for all you have done to help me.

Marcos Hernandez Mon, 06/22/2009 - 22:56


Please keep this kind of feedback coming. I can't promise we will deliver every time, but we will do our best. It is our charter to listen to our partners and help them be successful.

Thanks for the candid comments.


mcastrigno Mon, 06/22/2009 - 21:08


Since what I am trying to do here is supported on a POTS line which I don't have, What about emulating a POTS line by routing (forwarding) my all incoming SIP trunk calls out one of my FXS ports and cabling that back into an FXO port?  Process the call with the T37 support that exits for POTS lines and then routing the call to the AA?

Would something like this work?


Marcos Hernandez Mon, 06/22/2009 - 22:50

This is actually the workaround. We don't usually propose it because of the implications and lack of elegance, but you can definitely do it.


mcastrigno Tue, 06/23/2009 - 07:09


What are the implications besides using more resources? Is there functionality that I won't be able to access?

Seesm like the UC500 will just think I have two trunks, one SIP one POTS and be unaware of the "abuse" I would be subjecting it to.


Steven Smith Tue, 06/23/2009 - 12:00

Yes, it would work.  But I think you would only get one inbound call at a time.  Since you are going to use FXO and FXS ports, you could roll them over with call forward busy, but again, you will run out of ports and then could have 4 calls.  (Could be 8 with expansion FXS on an 8 port FXO chassis).  Not really recommended.


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