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video phone via landline

My question may sound weird but I could not find a clue online and I am not in telecom field. Hoping I can at least get some expert insight here. Than k you very much in advance!

Assume there is no internet at all (not even ADSL or DSL), and no cell phon e next work at all. Is it even possible to make two video phones that commu nicate purely through landline? I mean, just "invent" video phone and simpl y replace your home analog phone, and video call another person who also re place his home analog phone with video phone. It is kind of like video int ercom but through landline (video intercom seems to use different wire), an d it is two-way video instead of one way video plus one way audio like vide o intercom.

What I learned is that, the analog voice signal and digital signal (I assum e video has to be digital) can both transferred through the first pair of w ire (T/R) in a landline. Analog signal and digital signal can be mixed beca use their frequency are very different. I understand that the bandwidth wil l be quite limited, but I am fine with only like 200x300 pixel sized pictur e, and with only 10 fps (frame per second) so hope bandwidth is not a real issue.

I also assumed there is no DSL or ADSL available, which means I cannot use the existing TCP/IP protocol but need to develop my own protocol just for d igital data transfer between two phones connected through a physical landli ne.

Is my idea even possible? I am thinking of this for seniors who are afraid of any internet and smart phone thing and all they have is just the old ana log phone and a landline.

Jason Yan

Reply to
Jason Yan
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There were, indeed, some of these available in 1995 or so.

Slow scan (maybe once/sec?) low quality images.

My boss had one on his desk and there were about a half dozen folk he could talk to and watch.

Reply to
danny burstein

Thank you for the answer, that is very interesting! Could you give me any m ore info so that I can dig more into it? like name of the product or compan y name, what principle it use, any key words for online searching, or if yo u still have a few the old units that I can buy them from you. Thank you ag ain!

Reply to
Jason Yan

Afraid not. Sorry. I saw some adverts for them as well, but again, this was 1995 or so. Maybe 1990.

Reply to
danny burstein

You may find this webpage re the history of AT&T's attempt at videophone service interesting. Especially at the end, it shows a 1990's deskset that apparently was sold by Sears, and may have been the unit that Danny Burstein referred to.

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Based on my (now retired) 30 year career in data communications, your challenge will be to create a video/voice digitizing scheme that can produce a usable picture & voice needing no more than 2400 bits per second data rate. There were/are dial-up modems that could create a

2400bps full-duplex data connection over the PSTN (Public Switched Network). But due to that 2 wire PSTN connection being limited to 3 Kilohertz of analog bandwidth, 2400 digital BPS Full Duplex pushed the limits of modem technology.

The ITU-T standard for these modems is "V.22bis" "V.22bis is an ITU-T recommendation extending V.22 with a faster rate using QAM at 600 baud to carry digital data at 2400 or 1200 bit/s. The

1200 bit/s mode is compatible with V.22."

Good luck.........

Reply to
""Retired"

Eyup, that sure looks like what my Big Boss had on his desk.

Thanks.

Reply to
danny burstein

Thank you so much! really appreciated! I searched and read a few articles a nd learned a lot about the ISDN, H.320, codec, etc. And I even found a comp any who still manufacture and sell the product:

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e/vproducts.htm Basically the videophone integrated a modem, video process ing chip, camera, etc. Price acceptable. I may buy two sets soon to try the m out. Also, it looks more accepted in German than in US. Germany Amazon is selling the videophone "Telekom T-View 100" at 200 euro.

Reply to
Jason Yan

Good to know. I might actually have a use for something like them...

(Once the economy resettles)

Reply to
danny burstein

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