TRANSATLANTIC TELEPHONY 



183 



two one-hundredths of a second during which time the switching 

 mechanisms have performed the operations just noted and have thus 

 put the circuit into shape for the voice waves to go forward. 



Fig. 14 shows the shifts in power level in going from one end of the 

 circuit to the other for a connection from San Francisco to London. 

 The zero of the scale corresponds to the power level at which power is 

 given out by an ordinary substation set when actuated by a loud voice. 

 The power ratios compared to this are shown at the right on a log- 

 arithmic scale. 



The comparatively small ups and downs in the power level cor- 

 responding to transmission over the wire lines represent, of course, the 

 line attenuations and successive amplifications by telephone repeaters. 

 The highest power level is naturally at the output of the radio trans- 

 mitter where it is about one hundred million times the starting level 

 At the English receiving station it has been dropped to about the same 

 ratio below the zero of the scale. 



Fig. 15 — Technical operators' position 



In view of the character of radio, in particular its variable nature, 

 the circuit is under constant supervision during operation by two 

 technical operators, one located in New York and one in London. 

 Fig. 15 shows the special terminal equipment, meters, etc., and the 

 technical operator at the New York end. 



