 lolwhatYou're getting warmerPremium
join:2001-06-11
PonziWorld
 ·Callcentric
2 edits | [CallCentric] [HT-286] outbound faxing problems I used to be able to fax outbound with minimal trouble; fax speed would drop all the way from 14400 to 4800, but they'd go through. Now, however, the connection will drop during T.30 setup.
The HT-286 settings are all default (including Fax Mode = T.38), except that the LEC (Line Echo Canceller) is disabled. The HP 640 fax machine's settings are the following (no idea which ones might be truly pertinent):
Forgot this tidbit: I did try to set Fax Mode to Passthrough (PCMU/G.711μ), but that didn't work either.
Also, as noted below, I had turned the Modem Speed all the way down to 2400, with similar results.
Come to think of it: I had a temporary DID through CallCentric while I waited for the Death Star to allow a port-out. That temporary DID was issued by Earthlink Business (Choice One), but the permanent DID was ported to Peerless Network. The faxing problems started around that time. Correlation isn't causation, but...
Modem Speed: 14400
Fax TX Level: -12dBm (can be between -15 and 0)
Fax RX Level: -43dBm (can be between -43 and -48)
CNG Count: 2 (can be between 1 and 4)
T1 Time: 55 (can be between 30 and 150)
Fax Error Rate: 10% (can be 5, 10 or 20)
Flash Time: 600 ms (can be 100, 280 or 600)
Pause Time: 3s (can be between 1 and 9)
Make/Break: 40/60 (can be 40/60 or 33/66)
Ring On Time: 15x10ms (can be between 0x10 and 99x10)
Ring Off Time: 60x10ms (can be between 0x10 and 99x10)
DTMF High Level: -6dBm (can be between -99 and 0)
DTMF Low Level: -8dBm (can be between -99 and 0)
USB Mode: Fast (can be Fast or Slow)
PWM Value Setup: 168 (can be between 100 and 208)
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PX EliezerPremium
join:2008-08-09
Hutt River
kudos:12 | Try setting the fax machine to 9600 instead. |
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lolwhatYou're getting warmerPremium
join:2001-06-11
PonziWorld | I had turned it all the way down to 2400 at one point, but it still would die. |
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| said by lolwhat:I had turned it all the way down to 2400 at one point, but it still would die.
I've previously tested baud rate extensively, and this lines up with my findings. It seems you want to get the data through as fast as possible. Making it go through slower only increases the chance a line or ecm octet will not get though in time when the next packet loss or jitter drop-out happens. You just don't want to use 33.6 super g3 fax, since that is v.34 which depends on good line quality to work. Even then, the 9600 or lower have less robustness against noise, something 14400 was designed to increase success over noisier lines. |
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PX EliezerPremium
join:2008-08-09
Hutt River
kudos:12 Reviews:
·voip.ms
·callwithus
·Callcentric
·Vitelity VOIP
·Optimum Voice
·Gizmo5
| I don't mean to doubt your experience but it sounds a little counter-intuitive, like saying if you can't see the road clearly at night, just drive faster because you'll be home sooner.... 
Anyway, for the general issue, here is one recommendation found in the official manuals for many of the HP machines:
● Start off with the fax set in V.34 mode and with Error Correction Mode (ECM) turned on. The V.34 protocol handles any changes in transmission speed needed to accommodate VoIP networks.
● If numerous errors or retries occur with the unit set to V.34, set V.34 Off and set Maximum Baud Rate to 14,400 bps.
● If errors and retries persist, set a lower fax speed as some VoIP systems cannot handle the higher signal rates associated with fax. Set the Maximum Baud Rate to 9,600 bps.
● In rare cases, if errors persist, turn off ECM on the product. The image quality might decrease. Ensure that the image quality is acceptable with ECM off before using this setting.
I would ask the OP, have you tried shutting off all of the T38/passthrough functions, and forcing the use of G.711u (PCMU)? I've sent outbound faxes this way. |
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PX EliezerPremium
join:2008-08-09
Hutt River
kudos:12 Reviews:
·voip.ms
·callwithus
·Callcentric
·Vitelity VOIP
·Optimum Voice
·Gizmo5
1 edit | reply to lolwhat
said by lolwhat:Come to think of it: I had a temporary DID through CallCentric while I waited for the Death Star to allow a port-out. That temporary DID was issued by Earthlink Business (Choice One), but the permanent DID was ported to Peerless Network. The faxing problems started around that time. Correlation isn't causation, but...
That possibility would seem relevant to receiving faxes (inbound), but not to sending them (outbound). |
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| reply to PX Eliezer
Re: baud rate, said by PX Eliezer:I don't mean to doubt your experience but it sounds a little counter-intuitive, like saying if you can't see the road clearly at night, just drive faster because you'll be home sooner.... It seems to work like this, in a simplified version g.711 is more than capable of handling any modem since the pstn uses g.711 as well. Say if we have jitter packets come in that are too great for the de-jitter buffers to compensate for every about 1 second. In that 1 second the audio is nearly perfect, so it should handle modems for that one second. We could just send data as fast as we can to get as much through in that one second before an error occurs. By slowing down the baud rate in that one second less data gets through and in a whole more data gets lost. Ecm mode will just re-transmit the lost data whereas turning off Ecm mode there will be error concealment going on, and dropped lines perhaps, but too big of an error causes pages to get cut in the middle or go missing altogether. Even through Ecm is retransmitting the lost data, with the lower baud rates more data has to be otherwise retransmitted, so my testing seems to conclude that lowering the baud rate to 9600 or lower has no meaningful improvement. Now when it comes to getting faxing working from not working at all again there's no meaningful improvement. It may be just the 14400 was designed for greater success in noisier lines, and that any improvement you get from the baud rate being lower is then lost due to the fact that 9600 and lower are older technology and hence don't handle noise as well. An interesting caveat I've learned from some white paper I've read is that since g.711's audio concealment causes some kind of sound to be inserted instead of a bit of silence, the modem will interpret it as noise and be able to better compensate. |
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| reply to lolwhat
Re: [CallCentric] [HT-286] outbound faxing problems said by lolwhat:The HT-286 settings are all default (including Fax Mode = T.38), except that the LEC (Line Echo Canceller) is disabled. The HP 640 fax machine's settings are the following (no idea which ones might be truly pertinent): Contrary to popular belief, in my testing I've found that fax is just fine with an echo canceler. It may be fine without it as well, but I've found in some instances the far end machine can hear echos of itself during training and cause it to fail. I'm leaning towards leaving the Echo canceler on. Do make sure Echo *Suppression* and silence suppression is off though. |
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 TrimlinePremium
join:2004-10-24
Windermere, FL | reply to lolwhat
Did you notify Callcentric that this DID would be used for faxing? I think you need to as they will adjust your outbound/inbound carriers. I did this, and mine works flawlessly. |
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