We are using a digital phone line, but our fax machine is analog.

Question

We are using Time Warner digital phone line. Our fax machine is not old, but it is analog. After months of working on it, I finally got the DSL filter hooked up, and the fax was working. We had phone line problems and the tech came by to fix it--when I wasn't here. He unpluged my work and can't remember how I go it to work. Has anyone had this problem before?

Answer 1

As far as I know Time Warner is Cable, not DSL. So I am curious to know why would you need a DSL filter. I really don't think that you do.

They call it a digital phone line, mainly for marketing purposes, but this should not confuse you. All the phones and faxes that you are familiar with, especially the cordless phones, are still using what they call an analog line. It's all about standards compatibility.

To try and summarize this answer: Time Warner should have provided you a modem or analog adapter to connect (2 of) your phones. You can use one of them for a fax.

The reason that the fax doesn't work so well is that they are using a technology called VoIP (Voice over Internet Protocol), not because you did not have the filter connected. VoIP was not designed to support fax transmission so it would usually work with short faxes, but might fail with multiple pages.

Answer 2

In addition to what the previous posters mentioned:

Fax will only work over digital phones (VoIP) if one of two Codec's are being used.  G.711u (also known as PCMU) is the only Voice Codec that will support Faxing.  That's because G.711u is the highest bandwidth Codec that can faithfully pass Fax tones.  High compression codec's, even though good for voice, cannot faithfully handle Fax tones and just won't work. So, check with your digital phone provider just to ensure your account is set for G.711u (or PCMU).

Ask your VoIP, or digital phone provider if they support T.38 Fax Codec.  T.38 is the only codec specifically designed to support real-time Fax.  It is not a voice codec like G.711u, and will only work as a Fax line.  For example, if your ATA phone adapter is a 2-line adapter, then conceivably the 2nd line could be configured to only work with T.38 Fax data.

And, of course, the ATA phone adapter you are using must itself be compatible with T.38 codecs.  (your service provider can confirm its capability, if supplied by them)

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Unfortunately, there are too many variables and unknowns to know where what the real problem lies.

1.

However, as a last ditch test, unplug all telephones from the digital phone line.

2.

Then plug in the Fax machine only to the phone adapter plug - nothing else.  

No other telephones should be plugged in. This will test operation with the Fax machine only with no other loads on the line.

3.

Set your Fax machine for minimum speed.  Lowest Fax speeds are most reliable over VoIP.

4.

During this test, turn off your PC, or at least unplug its Internet cable.  This will eleminate the PC as a source of bandwidth hogging... you only want to test the Fax machine and nothing else in the house using the Internet... not games, no file downloads, nothing but Fax over digital phone.

5.

If the above test works for Faxing, let me know.  Otherwise, there is really no further advice I can give.  

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Time Warner claims Fax will work over their digital phone service.  Although I note that they do not advertise it openly (thus I suspect it is not reliable option).  However, they do state in their FAQ's that Fax will work.

http://www.timewarnercable.com/Carolinas...

So, if my above tests don't work for you, you really do need to discuss the issue with Time Warner Customer Service:

http://www.timewarnercable.com/Carolinas...

Answer 3

Fax machines (and modems) have trouble over any non-analog line because its not a true steady stream of audio.

One of the best things you can do is to try to force the fax machine to a slower speed.  How this is done varies quite a bit from machine to machine, so I couldn't even guess how to do this without knowing what machine you have.

Just look through the manual for a line speed setting, sometimes called fax speed, and its usually expressed in terms of "bps" or even (incorrectly) "baud rate"

I've heard of some dsl filters helping this, but the real reason behind it is that there is a certain amount of signal degradation from the filter and that basically forces the fax to a slower speed anyway.  If you can do it manually it would be much better because the filter will also cause more errors and cause the fax to take even longer.