Prophecy into practice: the early rise of videotelephony

In 1993 BT launched a new product-a videotelephone. Its arrival had been prophesied in the latter half of the nineteenth century and, indeed, in 1930 Bell Telephone Laboratories in the USA demonstrated a two-way television system in which the subject was scanned mechanically by a light spot. However, the most extended-in space and time-two-way public television service, pre-war, was that managed by the German Post Office whose Berlin-Leipzig service cost DM3.50 for a 3 minute connection. Such early services were very limited and the prospect of a widely distributed commercial service had to wait until bandwidth compression techniques and wide-band optical-fibre communication networks were available. The author discusses these early systems