Sending Faxes without a land line in late 2018??.............

[Rick Law]

This is actually a good reminder to us technologist that technology isn't everything.

[Yeah, I researched these back then.  I had to explain why EDI was worth doing...]

There was a time (around late 1980's to 1990) when fax was everywhere, yet official documents (such as purchase orders, letter of intend...) were send via telex.  The world has yet to catch up operationally -- specifically, legal standing of said documents.  Telex has been around for decades and by then, the legal requirements were well developed thus better supported by legal codes.  Both national and (some) international laws made telex equal to that of a signed letter.  So, (depending on where you are)  if you get a fax for an order of 100,000 units and the guy backed out of the deal, you have no protection whereas, if you get the same order via telex, you have the legal equivalence of a signed purchase order and can sue the guy for default.

EDI started around just after WW II but not as widely used as telex.  By 1990, EDI (x12) caught up with telex and then some.  EDI gained legal standing with EDI Service Providers being a 3rd party proof.  You send an order via EDI, your EDI Service Provider has "data retain rules" and such data can show you did received said document as you claimed.  The sender's EDI provider also has collaborating data.  So it became easier to deal with legally. Around mid/late 1990, (I think Singapore was first, then Hong Kong and then the rest of the Asean ports) you could do port of entry custom via EDI custom declaration so processing begins before your ship even docked.  Email was popular then, but back then if you send Singapore Port of Entry an email of your Bill of Lading and expect them to process your cargo for entry, it would of course go no where.

Even today, with all the email, fax, whatever - By law, I have to bring a hard copy for some prescriptions before a pharmacy can fill it where as some prescriptions can legally be handled by fax alone.  (That hard-copy required prescription was for some post-operation heavy duty pain killer which contains Opioids).  Even my veterinarian(cat doctor) knows email sender id can be faked.  So my veterinarian takes (with caller ID) fax prescriptions from my other veterinarian (eye-specialist) but not prescriptions via email.  (Yeah, I have my local vet fill the eye-specialist prescription to save the long drive to the specialist.)

[vk6zgo]

Back in the day, Management decided it would be a wonderful thing if manned TV & Radio Broadcast sites sent a daily report to the appropriate State Headquarters.
To this end, we were supplied with Telex machines & a tape reperforator.
After a while, we discovered that, using the "reperf" we could make up template tapes with the repeating stuff, run them, stopping & adding the appropriate stuff for that day's report, as needed to produce a new tape for that day.
We got pretty slick with this & the Telex system was fast & reliable, very rarely needing a 'resend".

Management then fell in love with Faxes, & we had to use them instead.
This entailed, either using an old "clickety clack" typewriter, or writing the report by hand.

The real trouble started when we tried to send the Fax.
It would almost always fail on the first try, sometimes on every try.
Compared to the almost trouble free Telex, it was a nightmare.

[Smokey]

Welcome from 2020, all you fax users! 
I need to relocate a physical fax machine to a new office that has no POTS wiring, and they really don't want to have to pull any.  It looks like T.38 and an ATA is the way to go.

Anyone have a recommendation for an inexpensive provider with good T.38 support? 

[Cyberdragon]

Re: 'Linotype' machines, for the young or uninitiated...
It was a huge mechanical machine, like this...

where you typed what's going on the newspaper, on the keyboard labeled '1'.
As you typed each line, it would spit out molded lead bars into a stack, that had the text
reversed, as in the following image. (Still hot to touch for a while!!)...

When you had a whole page full, they were set up in a large tray, and a 100 ton press would
imprint a physical copy into a thick sheet (like very dense cardboard), called 'ElephantHide'.
In another machine, this was bent into a half circle, and a new mold made with a mixture of
lead, tin & antimony. (Limited expansion/contraction when hot/cold). 2 of these would make
a complete drum shaped circle, to print the pages on rollers.   
Now it's all computers, and special photo lithography, but still used not too long ago!!!

There's one of those operating at the Baltimore Museum of Industry, they would give away free casts of whatever you wanted and even had a bucket of worn out molds they would give away like Halloween candy (all way before Corona of course).

[newbrain]

It strikes me that an android app should exist that would just generate the tones for a fax and dump that over whatever the voice connection happens to be, but I couldn't find anything like that.

Having worked with the network implementation of fax over mobile networks, I can tell you this is not how it worked or how it can work.
The codecs used for voice are so different from what is needed for fax that it would be a pointless and frustrating experiment (the same goes even for simpler stuff, such as DTMF!).

What happened for fax (over GSM at least - I'm not even sure it's still supported nowadays!) is that the UE (the phone) would send digital data through the network, and suitable IWUs (interworking units) would generate the fax tones at the border between the mobile network and the fixed one (where voice was sent uncompressed).

It was a nightmare of a system for a number of different reasons, e.g., (IIRC): some timeouts in the fax protocols could be shorter than the latency through the network...

EtA: Crap, I just noticed it's an old post! Oh well...

[Smokey]

All good.  I resurrected it. 
It sounds like what you are describing is the T.38 system from what I've read.  The ATA boxes take the standard fax protocol, convert it to T.38 that can be transmitted, and then converts it back to standard fax on the other end.  I'm fine with that system if that's what works now.  My problem is just selecting service providers that are reliable.

[bingo600]

At one time i had more than 100 VoIP based T.38 fax sites , all running ok w. multipage fax'es.
I used Linksys SPA-2102 VoIP ATA units for the fax'es.

/Bingo

[madires]

A VoIP ATA and a VoIP telco supporting G.711 (a or µ law, whatever is preferred) is sufficient for FAX if you don't want to use T.38.

[bw2341]

I only follow VoIP as a hobbyist so take the following with a grain of salt. My only faxing experience is sending a few one-page faxes over G.711u passthrough. I picked up most of this from following the VoIP Tech Chat forum at dslreports.

https://www.dslreports.com/forum/voip

For VoIP providers, t38fax.com has come up. From the website, it looks like they try to cater to fax users. There is a list of T.38 providers at voip-info.org

https://www.voip-info.org/voip-service-providers-t38/

For hardware, voice gateways from "professional" suppliers (Patton, Mediatrix, Audiocodes) are supposed to be "better" than ATAs from (amateur?) suppliers (Linksys, Poly/Obihai, Grandstream).  If they are, I can't really tell from the datasheets. Unfortunately, few people have the expertise and resources to perform competitive testing of multiple devices for faxing. If your chosen faxing provider has preconfigured hardware available, you should use it.

Most brands do not make any quality claims in terms of fax performance. Just "T.38" on the datasheet does not tell you the capability, the quality of the implementation or the version level. For instance, some can fax at 33600 bits/s while others can only do 14400 or 9600. It took some digging though the full user manuals to find that out.

I did hear of one brand, Netgen, that claims to be better at faxing. Their Smart ATA product line claims to have a robust T.38 implementation and faxing optimized G.711u passthrough. I haven't seen any reviews that verify these claims.

Whatever device you choose, there are settings that may help with faxing. First, you need to disable Call Waiting because that will always disrupt the fax. For T.38 settings, follow the provider's recommendations for speed, redundancy and ECM. Generally, lower speed and more redundancy should help.

For G.711u passthrough, any echo cancellation setting should be off. Fax machines have their own methods to deal with echo and the data transmission is mostly unidirectional anyways. Jitter buffer length needs to be as high as possible and any adaptive or adjustable buffer setting needs to be off. This makes sense as fax machines were designed when digital phone lines were always TDM. Dropping or repeating samples to correct buffer overruns and underruns creates audio distortion that was never considered when analog modems were designed. Dynamically changing the buffer length would be even worse.

While researching this post I just read about a T.38 faxing option on Lexmark multifunction printers! This would eliminate the analog messiness on your end. Maybe your brand of printer has a similar option available.

[Smokey]

Dude.  That's a great post.  You are my new personal hero for the day!

I'll look into the Lexmark multifunctions.  There was talk about getting some new hardware anyway. 

[madires]

For hardware, voice gateways from "professional" suppliers (Patton, Mediatrix, Audiocodes) are supposed to be "better" than ATAs from (amateur?) suppliers (Linksys, Poly/Obihai, Grandstream).  If they are, I can't really tell from the datasheets.

Linksys' VoIP ATAs went to Cisco (hint: don't enable https - it's a desaster). Grandstream's ATAs run reliable and provide good performance. I'm able to get about 24kbps with a classic modem via G.711. Fax works also well if there isn't a grumpy fax machine at the other side. But this isn't anything new as we've seen this already back in the analog and ISDN days - some fax machines are picky. You can't go wrong with Audiocodes, but I think Grandstream can compete with them.

[Ranayna]

One tidbit regarding t.38 faxing directly build into printers...

I am a phone system admin at a medium sized company, and obviously also have to deal with faxing. Still, in 2020 
Most of our faxes are going out purely digital from a software fax. That is using a virtual CAPI Port that talks SIP with our Cisco Phone system, that then goes out via an ISDN PRI connection.
We also have some hardware faxes using Cisco ATA boxes 187, 189 or 191, connected to the phone system. Let me tell you, the now nearing 15 years in age ATA 187 still works best for this.

But on to printers. We have Canon Printers. And those also have the option to do T.38 over SIP directly. Of course this is a licensed option. But the kicker is, not only do you have to pay several 100 Euro for the license to fax over SIP, you *also* need the hardware fax module with the analog ports to actually do this 
An ATA costs around 100 Euro, the license was around 400 Euro if i remember correctly with a similar amount for the hardware module, so even if finnicky, using that inbuilt option is just too expensive.

[thm_w]

Had to fax the hospital to request records from them. Took ~1hr of trying multiple times, I'm guessing there is just the one fax machine on the other end.
But faxzero worked well, $1 for 10 page credits.