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Jason JohanknechtFlag for United States of America

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Intermittent fax problem incoming only

100% of outgoing faxes work.  Client knows this because confirmations must be given for the contents of the fax.

Recently incoming faxes are intermittent.  The fax will ring every time, but not answer all calls.  The client bought a new brother fax and the same thing happens.  The old was a Brother also.  I haven't been onsite personally, but the tech that was sent out I talked with personally while he was there.  We believe the fax is answering the call and going silent at point of answering.  On site he could not find a setting to leave the connection handshake audible (may not exist).  The fax machine will record NG on the failed incoming.  Theses faxes are not large, so memory should not be the issue.  Line quality was tested on local calls and works perfectly.  The phone company has tested everything and agrees it works perfectly.  All local faxes work 100% incoming.  

So the client has reached out to the senders which have problems and none are using any digital fax (Spectrum service for example) or fax services.  They all use physical fax machines.  They are long distance calls and we suspect the connection to the local (Centurylink) exchange may be the problem.  Centurylink is still investigating this problem.  We just updated them this morning with additional fax # to check from.  The phone cord has been replaced to the fax.  Centurylink has a outside filter on the phone line which has a DSL piggyback.  They tested the filter and feel that is not an issue.  One other business in town is having the exact same issue with no luck yet.

What else could be the issue?
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Dr. Klahn

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The fax is a Brother 2840.  I am looking through the manual, but cannot find anything about v.27 and lowering incoming speeds.
I found an article from Brother about basic transmission, which lowers the baud rate to 9600bps.  That is the lowest option.
The changes have made no improvement.  Next idea?
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Dr. Klahn

Buy an older fax machine at Goodwill, lock it down to 2400 receive, and see if the issue improves.
The old fax machine had the same problem.
Blimey, fax!

Put an analogue phone on the line with a double adapter... when the fax stops ringing pick up the phone... can you hear the fax, in which case the machine answered?

If not then one end dropped the call.

So now unplug the fax machine.  When the phone rings does it keep ringing for 5, 10 rings so then you know the other end keeps trying.

This time when the other end rings in answer the phone after 3-4 rings.  Does the other end keep screeching fax noises trying to sync?

Has somebody piggy backed an old fashioned monitoring for alarm system or anything else on the same line that could be interfering?

You could also find an old 56k modem and connect it up to Windows and have it receive the documents and print or save the files -- you could have IT answer the phone but physical machine send them still on the same line if needed.

That should prove whether your end is actually answering the call and you can rule out a problem with it noticing the phone ringing and the other end giving up.

Seriously though.... fax .... is this legal reasons or something?

I'd give pretty good odds that the DSL filter is the issue.  DSL filters cut high frequencies which is where the information is in high-speed fax.  This also causes signal phase twisting, and again that is where the information is in high-speed fax.

Unfortunately the only way to prove this for this one, particular, specific line is to discontinue DSL service on that line.
I have new DSL filters, I will swap it out and have them retest.  Centurylink said they already did this, but I did not see it happen.

Yes the fax answers the calls.  Somewhere after that is where the fax machines will drop the call for line quality.  Centurylink has tested multiple times and said no noise on the lines, not their problem.  Again this only happens on fax calls that are only long distance.  Centurylink was supposed to be looking into that further, but no update yet (And I have requested an update on the status).  
Not sure if Centurylink was able to find the problem or not, but the client is reporting that most faxes are now working.  Nothing else was done recently for troubleshooting.
Although none of my testing and changes resulted in any improvement, the providers were able to fix something on their ends and the faxing has improved.  Not 100% yet, but good enough.