Automatic Printing Equipment For Long Loaded 

 Submarine Telegraph Cables 



By A. A. CLOKEY 



Synopsis: The introduction of the permalloy loaded submarine cable 

 has presented the possibility of telegraph transmission at speeds several 

 times those obtainable on non-loaded cables and has made practicable 

 the operation of printer telegraph equipment. The present paper presents 

 the various factors which affect the design of operating equipment and 

 describes the apparatus which has been developed and used for a consider- 

 able period of time under service conditions. The transmission speed 

 attained may exceed 2,400 letters per minute. To a certain extent, the 

 detailed design of the terminal apparatus is controlled by the electrical 

 characteristics of the particular cable to which it is to be applied and this 

 type of equipment cannot, therefore, be completely standardized. 



General 



AT the time the development of the loaded submarine telegraph 

 cable was undertaken, non-loaded cables were generally being 

 operated duplex at signalling speeds ranging from 5 to 8 cycles per 

 second (160 to 260 letters per minute) in each direction. The trans- 

 mitting apparatus consisted of transmitters of the reciprocating 

 contact type controlled by perforated tapes and the signals were 

 received and recorded by the delicate moving coil type of amplifiers 

 (generally referred to as magnifiers), relays and siphon recorders which 

 produced a received signal record of such a character as to require the 

 employment of highly skilled operators to translate and type the 

 messages in final form. Except for a few trials, automatic printers 

 had not been applied commercially to the operation of submarine 

 cables, although the highly successful results which had been previously 

 obtained with multiplex printing telegraph equipment on land lines 

 coupled with the increasing demands made upon the cable systems 

 as a result of the World War had directed the attention of telegraph 

 and cable engineers to the need for applying automatic printing 

 telegraph methods to submarine cables. 



Preliminary studies of the characteristics of permalloy as a loading 

 material for long telegraph cables indicated that, through its use, 

 transmission speeds many times that of non-loaded cables could be 

 readily attained. As the then existing apparatus was incapable of 

 operation at the high speeds thus obtainable and the operating methods 

 in use were not suited to handling the greatly increased volume of 

 traffic over a single cable, it became apparent that new operating 

 methods and equipment would have to be developed if the full ad- 



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