"A new, experimental system devised by Bell Labs may make an old teaching tool more alluring. Called an electronic blackboard, it uses ordinary (and low-cost) telephone lines to send writing that is chalked on a pressure-sensitive surface to any remote point for TV-screen display. The audio portion of a lecture or other presentation can, if needed, be sent via a second phone line, using a portable conference phone available commercially. The system is being tried out at the University of Illinois."
-- Popular Science, June 1974