the field of science and technology encompassing the study of the theoretical basis of facsimile communication, the development of means of transmitting stationary, two-dimensional images over a distance through communication channels, and the creation of systems providing such communication; historically, it is included as one of the divisions of telegraphy.
In phototelegraphy, research is conducted on the conversion of optical images into electrical signals and the reverse conversion, the development of methods of recording images, the transformation of analogue information into discrete information, the development of mechanical and electronic scanning systems, and the evaluation of facsimile signal distortions during transmission and the elimination of such distortions. The development of phototelegraphy is dependent on advances in electronics, radio engineering, electrical engineering, and illuminating engineering. Future developments are related to the improvement of facsimile systems (for example, the equipping of such systems with automatic image receiving and recording devices), the development and introduction of equipment for transmitting color images, and increases in the speed of facsimile transmission.