"The device that was called a telescreen [consisted of] an elongated metal ball, similar to a dull mirror, which was part of the surface of the wall: it could be lowered but never completely turned off [...]. The telescreen received and transmitted simultaneously. Any sound that W. made above a low whisper would be captured: furthermore, for as long as he remained in the field of vision controlled by the metal plate, he could be, in addition to being heard, also seen [...]. One had to live (or rather, one lived, out of a habit that had finally become instinct) with the awareness that any sound would be heard and that, unless in darkness, every movement would be seen."
(G. Orwell, 1984, Mondadori, Milano, 1976, pp. 26 e 27).