294 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1955 



to be made of the transmission level at the output of each repeater at 

 any time. Other more complicated testing equipment provided at each 

 terminal will enable measurements to be made to determine whether 

 both amplifiers are functioning in each repeater. 



In the case of the deep-sea "snake"-type repeaters which transmit in 

 only one direction, an arrangement is employed in wliich each repeater 

 of the 51 in the one-way circuits has slightly different electrical char- 

 acteristics, determined by a quartz-crystal resonator, in the frequency 

 band above that used for the speech channels. This enables a selective 

 measurement to be made from the terminals to determine, in effect, how 

 well each of the individual amplifiers is functioning. Arrangements 

 are provided to insure continuity of the power circuit even in case of 

 the complete failure of the heater circuit in one of the vacuum tubes. 



CARRIER 



< 



EQUIPMENT 



HP 

 IFILTER 



LP 



FILTER 



POWER 

 UNIT 



SHORE STATION 



REPEATERS 



FIRST LAST 



POWER FEED 



GROUND PLATES 

 J- IN SEA -L 



HP 

 FILTER 



L P 

 FILTER 



CARRIER 

 > 



POWER 

 UNIT 



SHORE STATION 



ANODES CATHODES 



90 V 



6 HEATERS =33V 



ANODES 



J-JLJ^TLj. 



3 HEATERS =55V 



REPEATER POWER CIRCUITS 

 CLARENVILLE- SYDNEY MINES SECTION 



REPEATER POWER CIRCUITS 

 OBAN- CLARENVILLE SECTION 



Figure 8. — Basic power-feeding arrangements. 

 POWER FEED TO REPEATERS 



The arrangements for feeding power to the repeaters on the two sec- 

 tions are generally similar and involve the use of constant-current gen- 

 erators series-aiding, and designed so that both ends control the value 

 of the line current. It will be noted from figure 8 that at the terminals 

 the power currents are basically separated from the speech currents 

 by so-called high-pass and low-pass filters. These electrical circuits, 

 as the name implies, divide the currents in such a way that the direct 

 current necessary to feed the vacuum tubes at the repeater points, and 



