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