By the early 1840s, electric telegraphs had been invented that could either print marks on paper tape (as in Morse's apparatus) or print the letters of a received message on a sheet of paper (as in Bain's printing telegraph). The recording of transmitted signals led Bain to ponder on the possibility of sending and receiving the signals that delineated an image drawn or printed on paper. For this purpose the two-dimensional image would have to be analysed at the sending end of the telegraph link to generate a sequence of electric pulses, the pulses would have to be transmitted, and, finally, a two-dimensional image would have to be synthesised at the receiving end from the received pulses. In addition the two instruments that carried out these processes would have to have their scanning auctions synchronised.

Inspec keywords: telegraphy; history

Other keywords: electric pulses; picture telegraphy; two-dimensional image; Morse apparatus; electric telegraph; Bain printing telegraph

Subjects: Telegraphy