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.
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."