Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Ask HN: Why can't I send faxes from my phone?

news.ycombinator.com

Post reply on HN
Print view View original

31–40 of 168 posts

Re: Ask HN: Why can't I send faxes from my phone?

#31

Post by cosmotic »

TylerE wrote: post #24
talles wrote: post #19

Genuine question: why there are folks still using fax?

Because legally it's the same as a physical document. Which is not true for printouts, emails, etc. There is no technical reason for it to be so, but it is what it is. Fax is actually ancient tech, predating the phone way back into the telegraph days. https://en.wikipedia.org/wiki/Pantelegraph

Considering a fax is a print, I'm not sure what the printout comment is regarding.

The presence and non-exclusion of email/IP gateways show how backwards the law surrounding this is.

Re: Ask HN: Why can't I send faxes from my phone?

#32

Post by throwlaplace »

gumby wrote: post #13

The fax requires a 56KHz channel which has not been used for mobile telephony since the 1980s (when AMPS and GSM were developed. Before then it was just a radio link through an operator). That’s why you can’t use a high speed modem either. Some gsm phones had the ability to transmit a fax but they actually used a different protocol to talk to a fax gateway. I never saw one of these in the wild. I haven’t been in that…

>The fax requires a 56KHz channel

hmm so you're basically saying that fax machines only listen to data coming across on a 56KHz carrier wave? i guess that makes sense since the same device (a fax machine) can function both as a telephone and fax (and you'd need to distinguish in hardware which mode you were operating in upon "picking up the phone").

but what i don't understand is the telephony (i'm not a network engineer): when i make a phone call from either a fax or a phone isn't there, at this point in time, a hop through a digital connection? so doesn't some interchange between me and the person i'm calling ultimately decide what frequency carrier the receiver hears?

Re: Ask HN: Why can't I send faxes from my phone?

#33

Post by tjohns »

mattrp wrote: post #11
mceachen wrote: post #7

Earlier quoted context omitted.

HQ audio quality (over 4G) is markedly better than land lines, and the fax protocol has had error correction since digital formats were adopted in the 60s and 70s. https://en.m.wikipedia.org/wiki/Fax My Palm Pilot (with a CDPD backpack) and candybar 2G Nokia could both send FAXes. I suspect there's no demand.

Fax has an ip protocol called t.38 however it is inconsistently implemented. Most services still rely on g.711 - essentially uncompressed voice - for transmission of fax tones. However there is no guarantee the end to end call will be g.711 even if specified during call setup. There is an app called eFax - unfortunately the service is not free but I as a subscriber routinely fax over the phone when it’s the only way…

While G.711 is uncompressed (it’s the same codec used within the PTSN backhauls), it’s still not great for fax because the fax protocol doesn’t tolerate the jitter introduced by VoIP. (Reliable latency is the one big benefit to switched networks like the PTSN.)

As I understand it (and I could be wrong), T.38 solves this by emulating an independent fax modem on each side of the analog connection, and only sending the image data over IP as opposed to sending audio.

Re: Ask HN: Why can't I send faxes from my phone?

#34

Post by ken »

mceachen wrote: post #7
wmf wrote: post #3

The lossy compression on phone calls might prevent fax from working. Also, I don't know if you can route call audio from anywhere other than the microphone.

HQ audio quality (over 4G) is markedly better than land lines, and the fax protocol has had error correction since digital formats were adopted in the 60s and 70s. https://en.m.wikipedia.org/wiki/Fax My Palm Pilot (with a CDPD backpack) and candybar 2G Nokia could both send FAXes. I suspect there's no demand.

> HQ audio quality (over 4G) is markedly better than land lines

This is one of those facts that, no matter how many times I hear it or what proof is offered, I find it impossible to believe.

Re: Ask HN: Why can't I send faxes from my phone?

#35

Post by amelius »

gumby wrote: post #13

The fax requires a 56KHz channel which has not been used for mobile telephony since the 1980s (when AMPS and GSM were developed. Before then it was just a radio link through an operator). That’s why you can’t use a high speed modem either. Some gsm phones had the ability to transmit a fax but they actually used a different protocol to talk to a fax gateway. I never saw one of these in the wild. I haven’t been in that…

Perhaps someone could start a relay service.

Re: Ask HN: Why can't I send faxes from my phone?

#36

Post by vidanay »

throwlaplace wrote: post #32
gumby wrote: post #13

The fax requires a 56KHz channel which has not been used for mobile telephony since the 1980s (when AMPS and GSM were developed. Before then it was just a radio link through an operator). That’s why you can’t use a high speed modem either. Some gsm phones had the ability to transmit a fax but they actually used a different protocol to talk to a fax gateway. I never saw one of these in the wild. I haven’t been in that…

>The fax requires a 56KHz channel hmm so you're basically saying that fax machines only listen to data coming across on a 56KHz carrier wave? i guess that makes sense since the same device (a fax machine) can function both as a telephone and fax (and you'd need to distinguish in hardware which mode you were operating in upon "picking up the phone"). but what i don't understand is the telephony (i'm not a network engi…

I seem to recall some occasions in the early 90's where there was exactly this problem and fax was not guaranteed to work with some land line due to the digital nature.

Re: Ask HN: Why can't I send faxes from my phone?

#37

Post by gambiting »

talles wrote: post #19

Genuine question: why there are folks still using fax?

It seems to be the same as cheques and magstrip-only cards - uniquely American thing that rest of the world hasn't seen in years.

I do remember not that long ago opening an apple developer account required filling out a form with your card details and faxing it to some US-based number. It was madness back then already.

Re: Ask HN: Why can't I send faxes from my phone?

#39

Post by kristopolous »

talles wrote: post #19

Genuine question: why there are folks still using fax?

I'm waiting for faxing to come back like cassettes:

Artists draw pictures and robodial a secret fan list (through a POTS modem and some 90s software) of fax machines where insiders can get exclusive limited physical copies of the art and the copies with the earliest timestamps become the most valued.

People will just be sitting around their house and they hear the fax machine starting to unexpectedly print something on a Saturday afternoon. Then, like some tactile version of a phone alert, they slowly watch the paper slide out of the machine with the latest artwork.

The lost joy of anticipation in the 30 or so seconds of waiting as you see the thing slowly form in front of you, recaptured once again.

Alternatively they hear from their friend that a new artwork is out and they anticipate going home and checking the tray of their fax machine to see their own copy.

This should be a thing, it sounds fun

Re: Ask HN: Why can't I send faxes from my phone?

#40

Post by toast0 »

cosmotic wrote: post #31
TylerE wrote: post #24

Earlier quoted context omitted.

Because legally it's the same as a physical document. Which is not true for printouts, emails, etc. There is no technical reason for it to be so, but it is what it is. Fax is actually ancient tech, predating the phone way back into the telegraph days. https://en.wikipedia.org/wiki/Pantelegraph

Considering a fax is a print, I'm not sure what the printout comment is regarding. The presence and non-exclusion of email/IP gateways show how backwards the law surrounding this is.

The law is not based on reality.

If I sent you a fax, and your fax machine (of whatever type) printed it out, that copy is legally as good as the original.

If I scan, then email, and you print it out, it is not legally as good as the original.

It doesn't matter if it makes sense, it is what it is.

Post reply on HN