Electronics > Projects, Designs, and Technical Stuff
1200 baud data transfer over audio passband of cellphone. Is that possible?
coppice:
--- Quote from: tooki on November 04, 2019, 09:45:26 am ---
--- 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.
--- End quote ---
Why do people make up rubbish like this?
tooki:
--- Quote from: coppice on November 04, 2019, 06:20:24 pm ---
--- Quote from: tooki on November 04, 2019, 09:45:26 am ---
--- 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.
--- End quote ---
Why do people make up rubbish like this?
--- End quote ---
The possibility of inaccurate recollection (as explained above) is not the same as “making up rubbish”. (And absent documentation either way, I’m not certain that my memory is actually wrong.)
Edit: documentation found, thanks to ollopa remembering the specifics. So yeah, I was right. Definitely not "rubbish", and definitely not "made up". (Also, how much more could I have couched it in uncertainty? I made it clear that I wasn't 100% sure, prefacing it with "AFAIK" and only saying that "something" got changed.)
ogden:
--- Quote from: coppice on November 04, 2019, 06:20:24 pm ---Why do people make up rubbish like this?
--- End quote ---
Nah. We are all guilty of "imprecisions" here, in this same discussion. No need to start flames.
ollopa:
It's not rubbish. One of the early phases of dial-up negotiation is signaling to the channel (AKA phone company) to disable echo cancellation for full-duplex operation. That's completely in-line with "the landline network has the ability to detect modems and change something in the codecs to make them work."
westfw:
Iirc, the old 1200bps modems required some sort of phase shift modulation, rather than just fsk.
(For bi-directional, anyway. The older 1200/150bps modems may have used straight fsk.)
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