Electronics > Projects, Designs, and Technical Stuff
1200 baud data transfer over audio passband of cellphone. Is that possible?
tooki:
--- Quote from: sv3ora on October 30, 2019, 08:42:55 am ---Do you think that I could pass the 1200 baud 1200Hz/2200Hz through the wired telephone instead, or will I have the same problems as the GSM?
--- End quote ---
Should work fine. AFAIK, the landline network has the ability to detect modems and change something in the codecs to make them work. Fax machines have relied on this for decades.
ogden:
--- Quote from: tooki on November 04, 2019, 09:45:26 am ---AFAIK, the landline network has the ability to detect modems and change something in the codecs to make them work. Fax machines have relied on this for decades.
--- End quote ---
Really? Citation needed. My knowledge about landline codec (G.711) say that they do not "detect modems". I talk about landlines of modem/fax era, T1/E1 circuits.
GeorgeOfTheJungle:
Last time I tried (maybe 10 years ago) I could not fax from my land line anymore. The FAXes are a thing of the 80s!
ogden:
--- Quote from: GeorgeOfTheJungle on November 04, 2019, 10:09:41 am ---Last time I tried (maybe 10 years ago) I could not fax from my land line anymore. The FAXes are a thing of the 80s!
--- End quote ---
Yes, so true. Today (cheap) telcos happen to use low rate codecs in their (mostly SIP) long haul trunks. On mobile networks you can literally hear cheap telco operator.
BTW I noticed "landline" solution which is made out of cellular/LTE terminal box with landline phone attached. Telco did not even bother to add any kind of UPS function, so your "landline phone" works only when you have mains electricity. :palm:
tooki:
--- Quote from: ogden on November 04, 2019, 10:04:29 am ---
--- Quote from: tooki on November 04, 2019, 09:45:26 am ---AFAIK, the landline network has the ability to detect modems and change something in the codecs to make them work. Fax machines have relied on this for decades.
--- End quote ---
Really? Citation needed. My knowledge about landline codec (G.711) say that they do not "detect modems". I talk about landlines of modem/fax era, T1/E1 circuits.
--- End quote ---
Oh gosh, it’s just a random thing I read or heard somewhere ages ago.
I don’t know what the magic search terms are to find out accurately. (Every search result about codecs is talking about VOIP, making it hard to find the docs from before that.) The closest I got is this, which is already VOIP era: https://www.eetimes.com/document.asp?doc_id=1201937
Maybe that’s what I heard, but I thought something similar applied to the PSTN, especially for long distance, where heavier compression was used, but fax still worked.
--- Quote from: GeorgeOfTheJungle on November 04, 2019, 10:09:41 am ---Last time I tried (maybe 10 years ago) I could not fax from my land line anymore. The FAXes are a thing of the 80s!
--- End quote ---
You would think, right?? But apparently in some countries and/or industries, they’re still widely used, especially in jurisdictions where faxes are considered legal documents, but emails and other internet transmissions are not.
I haven’t had a fax-capable device (ignoring my vintage computers with modems) since the 90s when I was living with my parents, so even when I had a landline of my own (which also has been a long time), I never had a chance to try faxing on it.
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