THE FACSIMILE MACHINE Although the facsimile machine was invented in the 1840s, it remained largely a device used in the newspaper industry for the transmission of pictures until the mid1980s. There were several reasons for this; some were technical and the others commercial. The technical problems which held up the development of the fax machine are illustrated in Figure . For simplicity we use the letter H and assume that scanning is carried out horizontally from the top left side to the right. . | Telecommunication Circuit Design Second Edition. Patrick D. van der Puije Copyright 2002 John Wiley Sons Inc. ISBNs 0-471-41542-1 Hardback 0-471-22153-8 Electronic 10 THE FACSIMILE MACHINE INTRODUCTION Although the facsimile machine was invented in the 1840s it remained largely a device used in the newspaper industry for the transmission of pictures until the mid-1980s. There were several reasons for this some were technical and the others commercial. The technical problems which held up the development of the fax machine are illustrated in Figure . For simplicity we use the letter H and assume that scanning is carried out horizontally from the top left side to the right. The scanning head then moves to the second line and the process is repeated. Again for simplicity the scanned field is divided into a matrix 20 by 20. Thus 400 pieces of information have to be sent to the receiver in order to reconstruct the H. The first task is to measure the level of light reflected or produced by each square and to assign a value of 1 or 0 we assume here that a 1 is assigned when a square is white and a 0 when it is black the opposite would work just as well . Figure b shows the result. Each one of these pieces of information is called a pel which is a pixel with its gray scale or color information placed in two categories black or white depending on its relative brightness . For the transmission to be successful the transmitter has to tell the receiver precisely which squares are to be left white and which are to be made black. In other words the read head in the transmitter and the write head of the receiver must be exactly on their corresponding squares at the same time that is they must be in synchronism and in phase. To obtain synchronism two pendulums of the same length with a mechanism for keeping them in phase were used 1 . The pendulum was not very practical because it had to be made quite large to store enough energy so that the losses during the .
