TELEPHONE SYSTEM OF THE UNITED STATES 67 



transmission from a group of telephone officials in New York to a 

 group of people interested in communication assembled for the pur- 

 pose in London. The success of these experiments led to cooperation 

 with the British Post Office and the establishment in 1927 of telephone 

 service between New York and London. This service has now been 

 extended to include the greater part of the telephones of North America 

 and Europe. 



As indicated in Fig. 53 there now exist one long-wave and one short- 

 wave telephone circuit between the two continents. A second short- 

 wave circuit will be placed in service about June 1 of this year and 

 a third in December. By the end of 1933 it is expected that there 

 will be in service between New York and London a group of six cir- 

 cuits consisting of three short-wave radio circuits, two long-wave 

 radio circuits, and one cable circuit. Our best information indicates 

 that the short-wave circuits will be suitable for service at least 60 

 per cent of the time, the long-wave, 90 per cent, and the cable, 100 

 per cent. 



Since the beginning of 1929, the average number of messages handled 

 per week has been 275. For this period the average number of mes- 

 sages per day, omitting Saturday and Sunday, has been 44. Eighty- 

 nine messages were handled on Christmas Day, 1928. 



Certain technical features of these circuits are particularly inter- 

 esting. The long-wave circuit operating at a frequency of approxi- 

 mately 60,000 cycles employs the "single side-band carrier suppres- 

 sion " method. This appears to be the only use of this method in 

 radio, although it is widely used in " carrier " circuits over telephone 

 wires. The energy saved by the suppression of the carrier and the 

 increased selectivity permitted by the narrow band of frequencies 

 which is transmitted gives this system a transmission efifectiveness 

 as great as a system of three or more times as much power using the 

 ordinary transmission method. At both ends the receiving stations 

 are situated as far north as can conveniently be reached and use is 

 made of highly directive receiving. It is estimated that at the United 

 States end these two factors represent an improvement equivalent to 

 an increase in power of five thousand times as compared to a non- 

 directive receiving station located at the same latitude as the trans- 

 mitting station. 



The short-wave transmitting and receiving stations located not far 

 distant from New York and London employ highly directive antenna 

 systems. The design of such antennas must take into account eco- 

 nomic factors and possible reactions on receiving effects other than 

 power efficiency such as fading. The improvements effected by such 



