558 



BELL SYSTEM TECHNICAL JOURNAL 



Application to Picture Transmission 



However, if in order to utilize fully the line-frequency-range we 

 introduce the process of recording, our message no longer exists 

 throughout its transmission as a magnitude-Z^we function, but becomes 

 a magnitude-5^ace function. Also in the case of picture transmission 

 the information to be transmitted exists originally as a magnitude- 

 space function. We may, of course, regard either a phonograph record 

 or a picture as a secondary symbol, and say that the information 

 transmitted consists of the sender's selection of a particular record 



Fig. 6 



or picture to which he desires to call the attention of the receiver. 

 The information involved in such a selection is then measured by the 

 logarithm of the number of different records or pictures which he 

 might have selected. The problem then is to analyze the magnitude- 

 space function which constitutes the secondary symbol into a sequence 

 of primary symbols. This may be done in a manner similar to that 

 already employed for magnitude-time functions. 



The case of a phonograph record is directly analogous to those 

 already considered in that the magnitude is a function of the distance 

 along a single line. This distance is therefore analogous to time and 



