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

121–130 of 168 posts

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

#121

Post by tinus_hn »

DonHopkins wrote: post #111
orf wrote: post #110

Earlier quoted context omitted.

There are several apps on the App Store that allow you to do just that?

For a fee (which Apple gets 30% of). The point is that there was no reason for Apple to insist I send them a Fax to join their developer program, but they did anyway. I guess somebody at Apple thought it was more "business like" to introduce another hoop to jump through to make it harder to join the developer program, because just paying $50 was not enough.

It used to be that faxes had some kind of legal power emails did not, perhaps that was the reason.

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

#122

Post by kelnos »

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…

Wish this wasn't the highest-rated comment, as it's not correct.

If it needed a "56kHz channel", it would not have worked in the phone-over-copper-wire days either.

If we assume the parent meant 56kbps, that's still incorrect. The fastest fax machines use V.34bis modems (ignoring ISDN), which give you 33.6kbps, though many (most?) still support the oldest standard, V.27, at 2400bps!

The real issue sending a (T.30) fax over a cell phone line would be jitter and packet loss, since most cell networks are IP-based nowadays. T.30 is not very resilient to noise or timing issues. There's the T.38 standard, which was designed for sending faxes over a packet-switched network, but it's still sensitive to timing issues (esp. since often you'd be talking to a real fax machine on the other end, after going through a T.38/T.30 gateway).

Cell phones certainly don't give you the bandwidth that a copper landline does, but it'd certainly be enough to transmit a fax... if you could keep the error rate low enough... which I doubt.

(Source: I built the initial production version of Twilio's fax product.)

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

#123

Post by new2628 »

amelius wrote: post #35
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.

They exist and cost $10 for a couple of pages, as the OP said.

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

#124

Post by m000 »

tinus_hn wrote: post #121
DonHopkins wrote: post #111

Earlier quoted context omitted.

For a fee (which Apple gets 30% of). The point is that there was no reason for Apple to insist I send them a Fax to join their developer program, but they did anyway. I guess somebody at Apple thought it was more "business like" to introduce another hoop to jump through to make it harder to join the developer program, because just paying $50 was not enough.

It used to be that faxes had some kind of legal power emails did not, perhaps that was the reason.

I'd bet that any "privileges" faxes might had stem from the fact that they were automatically printed. This makes life a lot easier in a paper-backed office, so they made it a requirement to fax any "formal" communications.

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

#125

Post by kalleboo »

bawolff wrote: post #119
perl4ever wrote: post #83

Earlier quoted context omitted.

The thing is, when I'm asked to send sensitive documents over unencrypted email or something, then I'd rather use the fax option. And I don't trust any internet gateway, I go to some local store with actual fax machines. I kinda sorta think of it as more secure than the internet, still?

What type of threat model is this? Even standard unencrypted email is largely opportunisticly encrypted these days. Security properties of that is "debatable", but a fax isn't encrypted at all...

> Even standard unencrypted email is largely opportunisticly encrypted these days

I hadn't looked at Google's email encryption report probably since it came out, was very happily surprised to see it's over 90% now[0]. Still doesn't say anything about the issues with accepting self-signed certificates etc though.

[0] https://transparencyreport.google.com/safer-email/overview

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

#126

Post by AnssiH »

LeoPanthera wrote: post #21

This used to be possible over GSM, at least in the UK, and so I assume most places that use(d) GSM. I did it from various generations of the Nokia Communicator. The phone would initiate a special kind of phone call (from memory, the same AT string used to start an ISDN connection) and then send digital data over the link, not audio tones directly. This would emerge onto the analogue phone network as fax tones. I supp…

Yeah, I had fax on my mobile plan in Finland as well (and if it just requires CSD I'd guess it still works). Never had any use for it, though.

There was also an optional assigned special phone number to have it work in reverse (receiving faxes via your connection).

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

#127

Post by PunksATawnyFill »

rubatuga wrote: post #84
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 This is quite wrong. I believe you are confusing Hz with bitrate, as the most advanced modems communicate at 56kbit/s using PCM. To clear it up, a regular phone line has a 4000Hz bandwidth. With digital lines, you require sampling at at least 8000Hz (Nyquist theorem). It's impossible to send a frequency above 4000Hz using this line. Each sample is considered to have 7 usable bits of…

I figured that audio compression on mobile networks prevented the sending of faxes as tones.

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

#128

Post by ivanhoe »

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…

Copper wire has a lot of bandwidth, but traditional phone lines had low-pass filter at 4KHz, so anything above is cut off. Between switching stations signal is modulated and multiplexed, but on the receiving end it is again restored to the original analog signal. Therefore fax-machines couldn't possibly expect anything on 56KHz for sure, it would never get to them. Also, faxes make that well-known noise when establishing connection, and if it were around 56KHz, we wouldn't be able to hear it - anything above 15KHz is very hard to hear for adults. So the OP probably meant 56kbps as a transmission rate, which again is not true because faxes existed much before 56K was possible and many worked on as low rates as 2400bps.

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

#130

Post by kristopolous »

battery_cowboy wrote: post #106
kristopolous wrote: post #39

Earlier quoted context omitted.

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…

You do it and I'll be the first subscriber, as long as i can afford it :)

I'm not really an artist but ok sure. I can certainly fax some doodles. I'll think about how to pitch and present it. I'll register artsyfax.com this week and throw something together. I even have a pnp modem and a pots line.

There's probably Linux fax software nobody has used in 15 years that can import vcards and be scripted with lua or something.

Post reply on HN