ROUTE SELECTION AND CABLE LAYING 313 



Staffing for testing was provided by crews of 2 or 3 trained engineers 

 located at the transmitting cable station and on shipboard. Those on 

 the ship served 4| hour watches at 9 hour intervals, which permitted a 

 reasonable amount of rest and avoided continuous "dog watch" duty 

 by any one crew. 



Close contact between shipboard and cable station crews was essen- 

 tial, and was achieved by means of cable and radio order circuits (or 

 "speakers"). Communication from shore to ship when the cable was 

 powered made use of the standard cable order wire circuit at the cable 

 station to apply a signal in the frequency band 16-20 kc. The signal was 

 demodulated and amplified aboard ship by a special stripped version 

 of this same gear. The radio order circuits employed special land anten- 

 nas and equipment, and for the most part the ship's standard single 

 sideband telephone set, although other equipment at medium frequency 

 was sometimes used for short distances. Radio telegraph with hand 

 keying was available for back-up when conditions were too poor for the 

 radiophone sets. 



Plans called for powering the cable at all times except when splices 

 were being made. This was necessary for the measurement program, of 

 course, but also provided additional assurance of safe laying of repeaters, 

 as the glassware and tungsten heaters of the vacuum tubes are more re- 

 sistant to damage when hot. Power for the first half of each crossing was 

 provided from the cable station. Beyond this point, the required voltage 

 would have become excessive and so the shipboard supply was inserted 

 into the series power loop and its voltage adjusted in proportion to 

 the amount of second half cable actually in the loop. 



Monitoring against the possibility of faults was accomplished by 

 measurement of a pilot tone at 160 kc, transmitted over the cable at 

 all times except when data were being taken or power was turned down. 

 Audibly alarmed limits were set on the measurement to indicate any 

 significant deviation in transmission. In actuality, all unanticipated re- 

 ceived alarms were found to have resulted from frequency or voltage 

 shifts in the primary shipboard supply for the measuring equipment. 



During the design of the system,- consideration of the misalignment 

 problem had indicated the desirability of splitting the cable for each 

 crossing into a number of sections, called ocean blocks. These contained 

 either 4 or 5 repeaters, and were 150 to 200 miles in length. In loading 

 the ship, the two ends of each ocean block were left accessible for con- 

 nection to the test room and for splicing operations. 



Measurements made in the spring of 1955 off Gibraltar had indicated 

 an unexpected change in attenuation called "laying effect",^ which re- 

 quired some last minute adjustment of the repeater section lengths. 



