In <6da72874-50b6-459b-aee8-dacd86125ef0@googlegroups.com> Jason Yan <yan.xxs@gmail.com> writes:

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?

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.


--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

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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. Thank you very much in advance!

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

What I learned is that, the analog voice signal and digital signal (I assume video has to be digital) can both transferred through the first pair of wire (T/R) in a landline. Analog signal and digital signal can be mixed because their frequency are very
different. I understand that the bandwidth will be quite limited, but I am fine with only like 200x300 pixel sized picture, 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 digital data transfer between two phones connected through a physical landline.

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 analog phone and a landline.

Jason Yan

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On Saturday, March 28, 2020 at 9:51:15 PM UTC-7, danny burstein wrote:

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.

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

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In <6b46b080-850b-44d7-bbf7-7820cf4cbb70@googlegroups.com> Jason Yan <yan.xxs@gmail.com> writes:

On Saturday, March 28, 2020 at 9:51:15 PM UTC-7, danny burstein wrote:

There were, indeed, some of these available in 1995 or so.
=20
Slow scan (maybe once/sec?) low quality images.
=20
My boss had one on his desk and there were
about a half dozen folk he could talk to and watch.

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!

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



--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

--- SoupGate-Win32 v1.05
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On 3/29/20 12:48 AM, Jason Yan wrote:

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. Thank you very much in advance!

Assume there is no internet at all (not even ADSL or DSL), and no cell phone next work at all. Is it even possible to make two video phones that communicate purely through landline? I mean, just "invent" video phone and simply replace your home analog

phone, and video call another person who also replace his home analog phone with video phone. It is kind of like video intercom but through landline (video intercom seems to use different wire), and it is two-way video instead of one way video plus one
way audio like video intercom.

What I learned is that, the analog voice signal and digital signal (I assume video has to be digital) can both transferred through the first pair of wire (T/R) in a landline. Analog signal and digital signal can be mixed because their frequency are

very different. I understand that the bandwidth will be quite limited, but I am fine with only like 200x300 pixel sized picture, 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 digital data transfer between two phones connected through a physical landline.

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 analog phone and a landline.

Jason Yan

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.

https://flashbak.com/the-fantastic-and-troubled-history-of-the-video-phone-404033/

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.........

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In <g7ydnUucbe_2Tx3DnZ2dnUU7-XHNnZ2d@giganews.com> "\"Retired"@home.com writes:

On 3/29/20 12:48 AM, Jason Yan wrote:

[snippp.. regarding videophones that could work over
regular phone lines]

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.

https://flashbak.com/the-fantastic-and-troubled-history-of-the-video-phone-404033/

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

Thanks.




--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

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On Sunday, March 29, 2020 at 9:53:05 AM UTC-7, "\"Re...@home.com wrote:

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.

https://flashbak.com/the-fantastic-and-troubled-history-of-the-video-phone-404033/
Good luck.........

Thank you so much! really appreciated! I searched and read a few articles and learned a lot about the ISDN, H.320, codec, etc. And I even found a company who still manufacture and sell the product: http://cicall.com/videophone/vproducts.htm Basically
the videophone integrated a modem, video processing chip, camera, etc. Price acceptable. I may buy two sets soon to try them out. Also, it looks more accepted in German than in US. Germany Amazon is selling the videophone "Telekom T-View 100" at 200
euro.

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In <8026ba78-3c07-49a1-be5e-be666f3c5c21@googlegroups.com> Jason Yan <yan.xxs@gmail.com> writes:

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: http://cicall.com/videophon= >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.

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

(Once the economy resettles)

--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)