Automatic Printing Equipment for Long Loaded Submarine Telegraph Cables

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 considerable 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 T the time the development of the loaded submarine telegraph cable was undertaken, non-loaded cables were generally beingoperated duplex at signalling speeds ranging from 5 to 8 cycles per second (160 to 260 letters per minute) in each direction. The transmitting 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.