OBiTALK Community

Hello. When attempting to call a fax machine, the incoming audio is very quickly "cut off" when the answering fax machine begins emitting tones. The line remains open, but no audio from the answering side is allowed through. This happens when using both Callcentric and voip.ms through my Obi202.

When calling the same numbers using softphones, everything appears to be fine.

I've been sending/receiving faxes on Vonage for over 8 years with an ancient ATA, so I know faxing over voip works. ;D

Does something need to be changed in my Obi202 to allow faxing through it?

???

Hi UserAsdf,

Here's a stab in the dark.

I wonder if the quick "cut off" is the OBI is misunderstanding the initial fax tones as some sort of DTMF.  If so, one thought is to try different options for the DTMFMethod under...

Service Providers -> ITSP Profile AorB -> General -> DTMFMethod ->

Also, do you know what codec is in use during these attempted fax calls?  During the call, if you check Status -> Call Status -> Audio Codec, it should tell you what codec is in play during the call.  I've heard of people having better success faxing with G711 on CC, and I've heard of people having better success faxing with T.38 on CC.  So, trying each might help figure this out. :)

pc44

Hello. This is what I suspected also, but I'm not sure what to do about it.

I've tried changing the DTMFMethod to both Inband and RFC2833, disabling all codecs except T.38, and trying both phone ports.

At all times, the call status page shows G711 is in use. I would try forcing T.38 if I knew how. :)

UserAsdf,

Sadly, I'm not sure how to enforce T.38 either and have been unable to find much documentation regarding the use of T.38 in the admin guide.  Additionally, I am not yet setup for T.38 and so cannot test this out just yet.  I hope to be ready for T.38 service within a month, as I have been really looking forward to this capability on the OBI202.

In the interim, here is a link to a thread on another forum (https://secure.dslreports.com/forum/r24975786-Other-T.38-not-working-with-CallCentric~start=54) that talks about T.38 success with CC, albeit they are using a SPA2102.  Still, it might offer some tips or insight into getting our OBIs working.

If you discover anything, be sure to let me know! ;)
pc44

From the admin guide. (http://www.obihai.com/OBiAdminGuide.htm)

QuoteThere are two Codec Profiles available on OBi devices.  They are selectable Per Trunk (SP1/SP2/SP3/SP4/OBiTALK). To select a codec as the preferred codec in this profile, set the priority of that codec to be highest among all the enabled codecs in this profile. Each of the SP1, SP2, SP3, SP4, and OBiTALK services can be assigned a codec profile in its corresponding configuration. The codec list to use when setting up a call on the underlying service is formed from the list of enabled codecs in the chosen profile and ordered according to the assigned priorities in the profile.

There is also a star code for forcing a codec on a per call basis.


Code25
Default = Force G711u Codec Star Code  *4711, Use G711 Only, set($Cdm1,3)

Code26
Default = Force G729 Codec Star Code  *4729, Use G729 Only, set($Cdm1,4)

And I believe someone had mentioned that a provider that does T.38 (Callcentric does) may be needed for reliable faxing.

What would be nice to debug any problems is a faxing endpoint that one can fax to and see what's received on the other end. As well as fax back so one can see the same.

Quote from: Ostracus on July 03, 2012, 10:26:27 PM
What would be nice to debug any problems is a faxing endpoint that one can fax to and see what's received on the other end. As well as fax back so one can see the same.

You can try these fax services out to test the fax machine.

Testing Your HP Fax Machine with the HP Fax Test Service
http://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&docname=c00259105

http://faxtoy.net/ (Check out their web page to see your sent fax.

http://faxzero.com/  (send and receive. Look at the PDF emailed to you)

I've "forced" G711a and G711u by adjusting priorities in the codec profiles and confirmed usage in the call status page. The problem persists.

The problem is the Obi202 is almost immediately cutting the answering side's audio when it begins emitting fax tones.

I hear the answering fax tone for about half a second, then the line goes "dead" on the answering side. This prevents a fax transmission from even beginning.

Is it possible I have a defective Obi202? Or could it be a known firmware issue?

HardwareVersion   1.3   help
SoftwareVersion   3.0.0 (Build: 3184M)

Thanks QBZappy, that'll help a lot.

Hi Ostracus,

Quote from: Ostracus on July 03, 2012, 10:26:27 PMThere is also a star code for forcing a codec on a per call basis.

Thanks for trying to help, but this does not apply to the T.38 in question.  Neither does the Star Code enforcement option.  Again, this is all according to the admin guide, which only mentions T.38 two times, one of which is on the title page. :D

Quote from: Ostracus on July 03, 2012, 10:26:27 PMAnd I believe someone had mentioned that a provider that does T.38 (Callcentric does) may be needed for reliable faxing.

You cannot use T.38 unless your provider supports it.


I'm looking for a way to select and force T.38 use.

Any thoughts anyone?
pc44

pc44,

One way I can think of doing it is to choose one of the Codec Profiles A/B to be exclusively for T38 (Fax codec).

For example Choose:
Codecs->Codec Profile A-> Disable all the codecs except the T38 codec. Assign that codec to the SP1/2/3/4 account you will be sending faxes with. Assign the other Codec profile to the remaining SP accounts you plan on using for voice calls.

QBZappy,

Great idea.  As alluded to earlier, I do not currently have a VoIP provider with T.38 support but hope to have that capability during the next month approximately.

In the meantime, I set my Codec Profile B to disable all Codecs, with the exception of T.38.  I tested this profile with GV on my SP4 (SP4 Service -> X_CodecProfile: B), and the call completed, albeit by kicking SP4 back down to G711U, (Call Status: tx=G711U; rx=G711U).

Perhaps the Codec Profile configurations do not apply to GV, because apparently even with the G711U Codec Disabled, the call is still placed using G711U.  If this is the case, I shall have to wait until I have a T.38 VoIP provider at my disposal to further test.

Thank you for this input!
pc44

Please note that the codec is limited to G711u only for all calls. In reference to GV in the admin guide.

Am I the only person having problems with the Obi202 silencing the answering end almostly immediately after the answering fax machine begins sending fax tones?

UserAsdf,

Forget about voipms. We've been there before. Voipms is useless for fax. Try forcing the T38 as I mentioned above and try again with CC.

I've already tried disabling all codecs except T.38 a few days ago. That resulted in an error message saying something about the service provider not supporting the call or something. I can't remember the exact error message. I can give it another try tomorrow for an exact error message. (Currently rushing out the door for festivities :))

I've been focusing on Callcentric since voip.ms doesn't advertise anything regarding fax capability. I did try voip.ms a few times out of curiosity. The same thing happens with both providers via my Obi202.

I've also submitted screenshots of my Obi configs to Callcentric, and they didn't find anything obvious to correct.

Both providers pass the answering fax tones perfectly (to my ears) when using softphones, so it's definitely an Obi issue.

I'm inclined to believe I have a defective unit, so I've already placed an order for a new one and I'll be sending this one back. If I find a solution before then, then I'll keep both. ;D

Have a look above. I have a post where you can test with several fax services. Give that a try.

Sorry, I guess I'm not being clear enough. I'll try again. :)

The fax never even begins transmission because the answering fax machine's tones are being cut off by the Obi202 almost immediately.

It's not a matter of fax quality or fax errors. The issue is the Obi not allowing the fax tones to come through on the line at all. I've tried multiple fax numbers.

UserAsdf,

I have reread your entries more carefully. You may still have a defective unit, however I can suggest a few other things to try.

Checklist
1) You are certain that that the Service Provider supports T38 codec? From this reply it doesn't sound like it. Just to be clear, was it the OBiMAN voice or a CC voice message?

Quote from: UserAsdf on July 04, 2012, 04:20:21 PM
I've already tried disabling all codecs except T.38 a few days ago. That resulted in an error message saying something about the service provider not supporting the call or something.

2) You obviously have followed the CC fax FAQ (http://www.callcentric.com/faq/30#205 )

Fax Machine: Try using the slowest possible speed on your fax machine. Normally 9.6k or 14.4k would be the best options, as speeds faster than 14.4k may not work properly with faxing. Disable error correction

T.38: Enable T.38.Disable echo cancellation and echo suppression. If available enable re-INVITE for faxes

Pass through:Try using the G711 codecs as these would offer more bandwidth.Disable echo cancellation and echo suppression Disable NSE, usually on Cisco/Linksys devices

Quote from: UserAsdf on July 02, 2012, 02:02:01 PM
At all times, the call status page shows G711 is in use. I would try forcing T.38 if I knew how. :)

I show a way how to force T38 codec up above. I assume you did the exact thing. You are certain that the fax is going over the CC trunk. I would try **1 or **2 before the fax number just to make sure you force it over the correct trunk. Since it shows using G711 it might be going over your GV account (if you have one, you didn't mention it).

Quote from: UserAsdf on July 04, 2012, 05:00:31 PM
The fax never even begins transmission because the answering fax machine's tones are being cut off by the Obi202 almost immediately.

I think that could be a symptom of many things including a codec issue, it may not have anything to do with a faulty OBi.

Failing the lack of proper Obihai documentation, I am forced to scavenge from other sources. We can find T38 Fax relay explained here: (May not be completely relevant to the OBi)

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_fax_services_over_ip_application_guide/t38.html#wp1158066

SIP T.38 Fax Relay

•The transport protocols specified in the ITU-T recommendation for T.38 are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). However, for T.38 fax relay on Cisco gateways, only UDP is supported for the transport layer.

•If SIP T.38 fax relay is not supported by both gateways, the T.38 negotiation fails and the call reverts to an audio codec. <-- NB This might be what is happening to you.

•T.38 fax relay requires a 64-kbps transmission rate, the same amount of bandwidth as a voice call with the G.711 codec.

•Fax Calling Tones (CNG) are optional and are not used to initiate a switch to T.38 mode. Instead, Called Station Identifier (CED) tones or preamble flags are used.

•SIP fax relay does not rely on NSEs to signal a switch to T.38 mode. Standard RFC 2543 and RFC 2327 SIP and SDP signaling are used instead.

•If the fax rate disable command is configured on a dial peer, neither the originating nor the terminating gateway can enter into Cisco fax relay mode, T.38 fax relay mode, or fax pass-through mode. The fax rate disable command disables fax transfer support.

Hope this helps. I'm surprised that someone else with a CC fax setup has not replied to you directly.

Hello, and thanks for re-reading my posts! :)

Quote from: QBZappy on July 05, 2012, 08:56:39 AM
1) You are certain that that the Service Provider supports T38 codec? From this reply it doesn't sound like it. Just to be clear, was it the OBiMAN voice or a CC voice message?

I've been using Callcentric for all of my fax testing, with the few voip.ms tests just to satisfy curiosity.

The error message came from the Obi device and not CC.

I disabled the following codecs when attempting to "force" T.38: G711u, G711a, G729, G726R32, iLBC

Quote from: QBZappy on July 05, 2012, 08:56:39 AM
2) You obviously have followed the CC fax FAQ (http://www.callcentric.com/faq/30#205 )

Fax Machine: Try using the slowest possible speed on your fax machine. Normally 9.6k or 14.4k would be the best options, as speeds faster than 14.4k may not work properly with faxing. Disable error correction

Windows 7 Fax & Scan won't allow me to change the fax or port speed of my usb faxmodem, but I'm not sure if that's relevant when fax negotiation never even occurs due to the answering fax tones being silenced by the Obi202.

Quote from: QBZappy on July 05, 2012, 08:56:39 AM
T.38: Enable T.38.Disable echo cancellation and echo suppression. If available enable re-INVITE for faxes

Pass through:Try using the G711 codecs as these would offer more bandwidth.Disable echo cancellation and echo suppression Disable NSE, usually on Cisco/Linksys devices

I attempted to call fax machines and confirmed both G711a and G711u were in use via the Obi202 call status page. Neither codec seemed to help.

I also sent screenshots of my config pages to Callcentric, and they couldn't find anything set incorrectly.

Quote from: QBZappy on July 05, 2012, 08:56:39 AM
I show a way how to force T38 codec up above. I assume you did the exact thing. You are certain that the fax is going over the CC trunk. I would try **1 or **2 before the fax number just to make sure you force it over the correct trunk. Since it shows using G711 it might be going over your GV account (if you have one, you didn't mention it).

I did confirm the calls were going over Callcentric both via the Obi202 call status page and by calling my own fax number hosted by Callcentric. (Doing the latter results in voicemail prompts)

I also sent a support ticket to Obi via this url a few days ago:
http://obihai.com/supportTicketForm.php

but I haven't received a response yet. I linked this thread url in the support request.

Quote from: UserAsdf on July 05, 2012, 01:44:41 PMWindows 7 Fax & Scan won't allow me to change the fax or port speed of my usb faxmodem, but I'm not sure if that's relevant when fax negotiation never even occurs due to the answering fax tones being silenced by the Obi202.

Hi UserAsdf,

It may not be relevant, but if you want to adjust the maximum port speed for your fax modem, on your Windows 7 PC, I would go to Control Panel -> System and Security -> System -> Device Manager -> Modems -> Your Modem.  Double-click on your modem entry.  This should open another window.  In this window, choose the tab marked "Modem."  Here you should see a Maximum Port Speed setting.  The thread that I referenced earlier regarding fax usage with CC suggested a speed of 14400; however, QBZappy's 9600 suggestion is probably a safer choice.

Again, it may not help, but I thought I'd just mention that.  Also, from the thread I reference earlier, if it turns out that your OBI is not defective, I do think your best route is to see if anyone at CC is willing to directly troubleshoot your situation.  As you are an active, paying customer of their service, they might.

Hope you get this eventually solved, :)
pc44

Quote from: UserAsdf on July 05, 2012, 01:44:41 PM
Windows 7 Fax & Scan won't allow me to change the fax or port speed of my usb faxmodem, but I'm not sure if that's relevant when fax negotiation never even occurs due to the answering fax tones being silenced by the Obi202.

This is for WinXP: (For Win7 see pc44 one post above this one)

This might be an important detail. Fax modems by default usually are set to go at the max speed of 115200 bd. To change the baud speed of the fax modem, you need to go to Control Panel, Administrative tools, Computer management, device management, look for the modem, look under properties, and look for a tab where the baud speed can be modified. There is the possibility that the speed can not be changed. Different manufactures allow modification of the com port and baud rate, others don't. You might get lucky. Have a look.


pc44
Son of a gun, I see you type faster than me  :D

Hello. Unfortunately, the port speed setting is greyed out and won't allow me to change it.

I'm really appreciating everyone's help btw, in case I haven't mentioned it yet. :)

UserAsdf,
Even greyed out, can you see what the baud speed is set at? If so what is it set at?

Another way to do it. Probably same result. What is the model name/number of the fax modem?

Changing the Modem Speed (Windows 7)

http://www.acs.nmu.edu/faq/index.php?action=artikel&cat=4&id=120&artlang=en

Quote from: UserAsdf on July 05, 2012, 01:44:41 PM

I did confirm the calls were going over Callcentric both via the Obi202 call status page and by calling my own fax number hosted by Callcentric. (Doing the latter results in voicemail prompts)

Callcentric, did you go to the "DID forwarding" tab and set the line to "Fax"?

Ostracus,

Quote from: Ostracus on July 05, 2012, 03:00:04 PM
Callcentric, did you go to the "DID forwarding" tab and set the line to "Fax"?

If this works UserAsdf owes you a beer.

The port speed is forced at 115200. The faxmodem is a USR Model 5637.

The instructions at nmu.edu appear to be for pre-configured dialup networks, or "dial up networking" as Windows calls it. I can't seem to find any of those windows on my system since I haven't used dialup since the late 90s. ;D

My DID is set to Fax in Callcentric and has been for a long time. :)

I've also confirmed fax reception to that DID a few days ago by sending a fax from faxzero.com.

Obihai responded to my ticket with a solution!

Quote from: Obihai Support
Please make sure that you disabled "SIP ALG" setting in your router.

It turns out "SIP ALG" was causing my problems. Once I disabled this on my router, I was able to send a fax ... from my voip.ms line!

I haven't tried sending via Callcentric (again) yet, but that's okay since I primarily use my voip.ms line for outgoing anyway. ;D

If anyone else runs across this problem and is using TomatoUSB firmware, the "SIP ALG" setting is in Advanced -> Conntrack/Netfilter -> Tracking / NAT Helpers -> SIP

Thanks everyone for all your help! :)

Yay Obihai !!!  Nice work. :)

This is terrific news... and yet another reminder to the rest of us... to continue to disable/stop/kill/terminate SIP ALG! >:(

Glad to hear this!
pc44

I just tried sending a fax via Callcentric and it was necessary to change the priority of the G711 codecs.

With G711u I still had the same problem I described where fax tones were being silenced.
With G711a everything appears to work fine.

Summary:
voip.ms appears to work fine with G711u. Callcentric needs G711a for faxing.

Just more notes for anyone searching this thread at some point in the future. :)

UserAsdf,

While you're at it, how about the T38 codec?

Quote from: QBZappy on July 05, 2012, 05:06:21 PMWhile you're at it, how about the T38 codec?

Indeed!!  I can't wait to get my setup up and running.  UserAsdf, if you decide to test out the T.38 at all and are successful, please keep us informed! :)

Thanks,
pc44

I haven't had a chance to try disabling all the codecs again to try and force T.38 yet. When the gf stops yelling at me for "playing with phone stuff all the time" I'll give it another try since I'm also curious myself. (I'll try to sneak this in later tonight 8))

I can say that I haven't seen T.38 show up on the call status page so far, and I've checked it religiously during testing up to this point.

I just tried to dial a fax number with all codecs disabled except T.38 via Callcentric. I received this error message from my Obi202:

"The number you dialed was rejected by the service provider. Reason is 415."

I think I remember reading somewhere the codec should automatically switch to T.38 during a call in progress if fax is detected? Meaning the call begins as G711 or even G729, then later switches to T.38 if both ends are happy? I could be wrong. ???

As I am reading this thread... baffles me why would one want to go through all this pain to send a fax through the fax machine, rather than use an online faxing service...
http://www.faxcompare.com/

Quote from: Felix on July 06, 2012, 10:46:33 AM
As I am reading this thread... baffles me why would one want to go through all this pain to send a fax through the fax machine, rather than use an online faxing service...
http://www.faxcompare.com/

Probably because all the hardware's paid for and the incoming DID can be free.

A few reasons. I'm sure everyone has their own.

• I only send a few faxes a year, but when I need to send it I don't want to drive 40 minutes to someplace to send them.
• I don't need to pay $8+/mo for something I use only a few times a year.
• It's nice not having to upload images or pdfs of my financial or personal info to some fax service.

I used Vonage for 8+ years and everything just worked - including fax. Excellent voip service, just too expensive in light of other options.

Now that I've figured out how things need to be setup with Callcentric and voip.ms via the Obi202, I won't need to play with those again. Hopefully. ;D

I'm faxing just fine using G711a (Callcentric) and G711u (voip.ms) now. I wouldn't mind seeing T.38 show up on my call status page though. :D

I was having a terrible time trying to fax through the Obi202 using GV. I disabled the SIP ALG in my router and was still no go. I was having the same problem where the tones would cut off before the handshake really got started. My solution was to use the extension on the fax machine to dial the number and to change my Brother MFC receive setting to fax/telephone. After dialing the number and hearing the beginning handshake, I hit send and the fax goes through with no problem. On the receive, the MFC answers and waits a second to see if the call is a fax or voice. This gives it enough time to hear the handshake and receive correctly. Yea!

I am having the same issue with Obi202.  It replaced an Obi100, which my faxing worked flawlessly via my Brother AIO, now I experience the same, where the responding party sends out its initial handshake tones, and then the audio gets cut-off while my fax keeps emitting the hello tones.  Never did anything with codecs or settings on the Obi100 it just plain worked via GV and lowering speed setting on the AIO.

I can't believe that the cheaper Obi100 seems to be less problematic than the Obi 202, this is now my second issue with this 'business' class model.  I used to be an Obi evangelist and have installed several overseas, but now not getting a good vibe...

EDIT:  Got it to successfully send to my Efax number as a test via GV after 2nd dial attempt, by disabling the T38Enable setting on the Obi202, that is unchecking the checkbox.  One less issue to contend with and confidence rebuilding... ;D

How about a plain-language tutorial for us newbies?  I experienced the same thing with my 202/GV setup: specifically, the call disconnects almost immediately after the fax machine emits its tone and the fax doesn't get sent.  I'd like to take advantage of all the knowledge in these posts, but it is over my head.  How would one go about "disabling the SIP ALG in my router" and/or "disabling the T38Enable setting on the Obi202?"  And how would one specify the use of G711a as opposed to G711u -- or has that requirement been OBEd by the latest discoveries?  Thanks.

I'm having this exact same issue with my 202, where the fax "handshake" is being cut off or "silenced" by the 202 a couple of seconds after it is initiated.

After reading through this thread I am trying to locate where I can uncheck the "T38Enable" setting but for the life of me cannot find it anywhere in my 202 expert setup.  Could somebody point me in the right direction please?

Thanks!

DChappell,

Welcome to the forum.

Find your way to the Codec pages, best do Codec Profile A and Codec Profile B. T38 is right at the bottom of the page.

Quote from: ianobi on September 13, 2012, 07:41:22 AM
DChappell,

Welcome to the forum.

Find your way to the Codec pages, best do Codec Profile A and Codec Profile B. T38 is right at the bottom of the page.

Thanks!!  One problem... I do not have anything about T38 in ANY of my Codec Profile pages. :(   Only codec's I've got are G711U / G711A / G729 / G726R32 / iLBC.  Currently the only codec's I have enabled are the G711U & A.

Maybe I've got an older firmware?  (jusst checked and I'm running the latest 3.0.0 build so that's not it)

That's odd! I have a OBi110 not a OBi202, so I can't check. I was looking at Codecs on page 147 of the OBiDeviceAdminGuide.pdf and there it is right at the bottom - T38Enable.

Interesting...  Just looking at the admin guide and it has a LOT more codec's listed that what I have access to via my ObiTalk Expert Settings...  Time to fire off a ticket to Obi.

Thanks!

Just checked - that's also true of my OBi110!

There are some cases of settings only being available by logging directly into the OBi via its IP address. Dial ***1 to get the ip address.

Uncheck the default box and then make your change, submit and reboot.

Of COURSE there are settings I can only get to by logging directly into the device... because that makes SOOO much sense right? LOL

Glad to report that disabling the T38 option has corrected the inbound fax issue, and thanks for pointing me in the right direction!

Forum support rocks!

Doug

Quote from: DChappell on September 13, 2012, 09:03:05 AM
Of COURSE there are settings I can only get to by logging directly into the device... because that makes SOOO much sense right? LOL

Glad to report that disabling the T38 option has corrected the inbound fax issue, and thanks for pointing me in the right direction!

Forum support rocks!

Doug

Ditto!  Found the T38 option and disabled it in Profile A and B.  Just tested inbound and outbound faxes and they worked perfectly.  I love this thing!

The only thing about disabling it is it makes you ask, "so why did I buy the Obi202, again"?

I have been fighting T.38 fax issues with callcentric for over a month.

The setting on Callcentrics site did improve outbound faxing with T.38 bit I'm still having issues with inbound faxes disconnecting. Obi techs told me the calls were disconnecting because Callcentric was issuing a BYE command. Callcentric has not told me the issue, but they are doing an internal port to a diffrent carrier.

http://www.callcentric.com/support/device/obihai/obi202

THANK YOU THANK YOU!!!!
SIP ALG was my problem too (after 4hrs of trying various settings).
Brilliant to bring the topic up and solving the problem.

I have mine as g711u and t38 , not sure which one was used
Will play around with other voip provider too (so far success with call centric, wanted to use the T38 feature...how do I know when T38 is being used?)

fathom,

A mini how to written by Billt928:
Re: FAX T.38
http://www.obitalk.com/forum/index.php?topic=3997.msg28737#msg28737

Thanks for the link.
I had to do some changes (trial and error because I would get a dial tone but it would not connect).
So now it's working: faxed from home (brother MFC-495W set at lower rate to obi202 via callcentric free outgoing per use service) to work (xmedius T.38 over ip fax company) and all 5 pages, including a PDF. Looks like it went through using the T.38

Duration   totall was 225 (this is a snapshot midway)
Direction   Outbound   Outbound

RTP Transport      UDP
Audio Codec      tx=; rx=G711U
RTP Packetization (ms)      tx=0; rx=20
RTP Packet Count      tx=192; rx=252
RTP Byte Count      tx=33024; rx=33384
Peer Clock Differential Rate      0 PPM
Packets In Jitter Buffer      0
Packets Out-Of-Order      0
Packets (10ms) Interpolated      5
Packets Late (Dropped)      2
Packets Lost      0
Packet Loss Rate      0 %
Packet Drop Rate      1 %
Jitter Buffer Length      110 ms
Received Interarrival Jitter      80 ms
DTMF Digits Received      0
Jitter Buffer Underruns      2
Jitter Buffer Overruns      0
Sequence number discontinuities      0
skew compensation      0 ms
send silence      0

Audio Codec      tx=; rx=G711U

From billt928 post:

You can tell your using T38 under call status (it does not show T38) but this line will change

Call Status
Audio Codec = tx=G711U; rx=G711U

Will change to when sending
Audio Codec = tx=; rx=G711U

or
Audio Codec = tx=G711U; rx=

when receiving a fax

spent many hours / days working with obi and callcentric on this.

The T38 reinvite uses a G711u tunnel  

That is why you loose the reference to G711u tx. T38 is negotiated in the G711u connection. if faxing a number that does not support t38 like google voice the Audio Codec will show tx=G711U; rx=G711U.
you should also notice some other differences in the call status info.

also changing ReInviteExpires from 10 to 15 seems to have helped a lot for me when faxing to another obi202. seems that devices negotiating T38 on both ends of the call cause more of a delay

Callcentric faxing so far working consistently.

VoIP.ms, not consistent at all (kids back from school so the router is working overtime with Netflix and other chatting)
This is from VoIP.ms who do not use T.38:
RTP Transport      UDP
Audio Codec      tx=G711U; rx=G711U