The transmission of pictures over telephone lines

THE problem of directly transmitting drawings, figures and photographs from one point to another by means of electricity has long attracted the attention and curiosity of scientists and engineers.1 The broad principles of picture transmission have been recognized for many years. Their reduction to successful practice, however, required, among other things, the perfection of methods for the faithful transmission of electrical signals to long distances, and the development of special apparatus and methods which have become a part of the communication art only within the last few years. Prominent among the newer developments which have facilitated picture transmission are the photoelectric cell, the vacuum tube amplifier, electrical filters, and the use of carrier currents.