AUTOMATIC PRINTING EQUIPMENT 403 



vantage afforded by the use of permalloy loading ^ was to be realized. 

 The development of the permalloy loaded cable was, therefore, 

 paralleled by a study of the newly presented operating requirements 

 and the development of suitable operating methods for high speed 

 loaded cables. It is the purpose of this paper to present the various 

 factors which affect the design of operating equipment for use on long 

 loaded cables and to describe the apparatus and principles of operation 

 which have been developed. The system which is to be described is 

 similar to the multiplex system now in use on American land lines ^ 

 but has been modified in several important respects in order to adapt 

 it to the requirements of cable transmission. 



The Cable and Amplifier as a Transmitting System 



Submarine cables have heretofore been thought of as transmitting 

 media which greatly distorted the signals and so reduced them in 

 amplitude as to require the use of a sensitive siphon recorder for 

 reception. The effects of signal distortion were, to a certain degree, 

 compensated for by the addition of sending and receiving condensers, 

 magnetic shunts at the receiving end, and, to a slight degree, by the 

 inherent characteristics of the siphon recorder itself. A separate 

 instrument termed a cable magnifier, of which there are several 

 different types, was inserted between the cable and the siphon recorder 

 to "magnify" the signal delivered to the recorder and thus partially 

 offset the effects of attenuation. No two cables are identical as 

 regards the distortion and attenuation of the signals and the means 

 which will effectively provide for the correction and amplification of 

 the signals on one cable will not necessarily be suitable for use on 

 another cable of different length or construction. The apparatus 

 provided for the correction of distortion in and amplification of the 

 received signals is therefore an essential part of a signal transmitting 

 system which includes the cable, and, except for the necessary switching- 

 arrangements, is independent of the means employed for impressing 

 the signalling impulses upon the cable and for producing a permanent 

 record of the corrected signals. Thus the development of terminal 

 equipment for loaded cables comprised two separate and distinct 

 developments, viz. the study of signal distortion and design of suitable 

 signal shaping amplifiers (described in a separate paper by Mr. A. 

 M. Curtis which appears elsewhere in this issue), and the development 

 of apparatus for delivering signals to the system comprising the cable 



^ O. E, Buckley, "The Loaded Submarine Telegraph Cable," Juiir. A. I. E. E., 

 June 26, 1925. 



■■'J. H. Bell, "Printing Telegraph Systems," Trans. A. I. E. E., Vol. 39, Fart 1, 

 1920. 



