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T38 Faxing with Auto Attendant


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Here is the issue we are running into:

- We have a number that is meant to be specifically for faxes

- but it gets voice calls on because it is listed in phone directories incorrectly


Currently the fax number is programmed into a specific extension in the PBX (ie ext has account number 499 561-xxx-bbb) for the fax machine which is attached to the PBX using a cisco SPA112 gateway which works fine, the calls come in from the same sip provider (ie same trunk) as our main voice dedicated lines


What we are trying to do is put an auto attendant on there so for people that call the line because of the bad listing they get a brief recording that briefly explains the listing error and asks them to press 1 to speak to a service rep (which then send them to the hunt group for the phones) and for the system to recognize faxes and send them to the ata instead of the hunt group


Current call flow:

- Voice Number is XXX-AAAA / Fax Number is XXX-BBBB

- Call comes in on trunk is routed based on the incoming DID

- for calls that are XXX-AAAA calls are routed to hunt group 300

- for calls that are XXX-BBBB calls are routed to fax ata 499


Proposed call flow:

- Call comes in on trunk and is routed based on DID

- for calls that are XXX-AAA calls are routed to hunt group 300

- for calls that are XXX-BBBB calls are routed to auto attendant 320

- Attendand plays recording offers to press 1 to speak to user

- attendant menu structure: 1 = 300 / F = 499


We setup the proposed call flow and

- if we call the fax number from say a cell phone or other land line we get the attendant if we press 1 we get the hunt group without issues

- if we call into the system from a fax machine the blf light for for CO line lites up and starts blinking and the call log shows its hitting the attendant but the call is never routed to the ata. according to the sip router we have all the inbound calls routing through the call is being routed to our PBX and media type is t38 / PCMU8000, and the call just shows as ringing

- if we disable t38 on the trunk at the provider and call in from a fax machine the attendant plays on the line for a second and as soon as a fax tone is heard it stops and routes the call to the ata, however because its not using t38 the faxes have a failure rate of about 8 out of 10.



the provider we are using does t38 and they do detection on their end so the call coming into the PBX has the codec set to t38 already

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