HIGH-SPEED OCEAN CABLE TELEGRAPHY 



255 



of sending. This is accomplished by driving from the multiplex 

 distributor a reversing mechanism which switches the cable from 

 sending eastward to sending westward or vice- versa at regular intervals 

 without the loss or mutilation of a character on any channel. To 

 adapt the apparatus to the demands for trafihc, the intervals of reversal 

 are made capable of variation over a considerable range so that the 

 system can be used, for example, alternately one minute eastward 

 and ten minutes westward or three minutes eastward and three minutes 

 westward, only about five seconds being lost at each reversal. 



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WESTERN 

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B 



Fig. 11 — Sent and received signals. A, Signal, sent at speed suitable for plain 

 relay operation; B, Received signal shaped for simple relay; C, Signal sent at twice 

 speed oi A; D, Received signal shaped for vibrating relay. 



(These records were made in the laboratory with an artificial line and accordingly 

 do not show the interference which would be present in the case of a cable operated 

 at maximum speed.) 



To secure the maximum speed of operation, use is made of the 

 "synchronous vibrating relay," a method of signal restoration de- 

 veloped in the course of our laboratory studies of apparatus for 

 loaded cables. The synchronous vibrating relay takes advantage of 

 the principle of the Gulstad vibrating relay, which has been extensively 

 used on both land-lines and cables, but possesses a further advantage 

 in that use is made of the synchronous multiplex distributor to secure 

 the most effective application of this principle. 



To describe and explain the circuits and apparatus of the syn- 



