Such an antecedent usually consisted of two closed-circuit television systems connected via coax cable or radio.
An example of that was the German Reich Postzentralamt (post office) video telephone network serving Berlin and several German cities via coaxial cables between 19.
By reducing the need to travel to bring people together, this technology also contributes to reductions in carbon emissions, thereby helping to reduce global warming.
The concept of videotelephony was first popularized in the late 1870s in both the United States and Europe, although the basic sciences to permit its very earliest trials would take nearly a half century to be discovered.
The development of the crucial video technology first started in the latter half of the 1920s in the United Kingdom and the United States, spurred notably by John Logie Baird and AT&T's Bell Labs.
This occurred in part, at least with AT&T, to serve as an adjunct supplementing the use of the telephone.
This technique was very expensive, though, and could not be used for applications such as telemedicine, distance education, and business meetings.In 1995 the first public videoconference between North America and Africa took place, linking a technofair in San Francisco with a techno-rave and cyberdeli in Cape Town.At the Winter Olympics opening ceremony in Nagano, Japan, Seiji Ozawa conducted the Ode to Joy from Beethoven's Ninth Symphony simultaneously across five continents in near-real time.During the first manned space flights, NASA used two radio-frequency (UHF or VHF) video links, one in each direction.TV channels routinely use this type of videotelephony when reporting from distant locations.