[vidarh]

You can find some info here [1],[2]

Of course this was far technically simpler than "proper" video telephony, as they required dedicated point to point circuits rather than function over a regular phone line. Most of the effort to popularise video-telephony was not the concept itself, but solving the engineering challenges of making it work over the regular phone network and making the devices small and cheap enough. In that respect the booths at the '64 World's Fair would have been impressive demonstrations of progress toward that goal.

[1] https://www.warhistoryonline.com/war-articles/nazis-introduc...

[2] https://www.mirror.co.uk/usvsth3m/before-second-world-war-na...