156 BELL SYSTEM TECHNICAL JOURNAL 



The voice currents from the transmitters which were employed for 

 the ceremonies, after passing through amplifier A 2 , separated into 

 two branches, one branch going to the local amplifier B\, which sup- 

 plied the local loud speakers R lt the other going to the telephone cir- 

 cuit through amplifier C 2 , switch Si and amplifier C\. The switch 

 Si was provided for connecting either the announcing transmitter T\ 

 or one of the transmitters for picking up the ceremonies to the end of 

 the toll line. V\ and V2 are volume indicators, Vi being employed to 

 indicate that the proper power was being put into the toll line, while 

 V2 furnished an indication of the volume which was being delivered 

 by the projector group Ri. During the ceremonies the amplifier C\ 

 was continuously adjusted so as to deliver proper volume to the long 

 distance telephone circuit, the volume indicator V\ making it possible 

 to keep the volume applied to the toll line within close limits. At the 

 same time independent adjustments were made of the amplifier Bi 

 to take care of the varying conditions introduced by the different talk- 

 ing conditions as well as the varying conditions introduced by shift- 

 ing of the crowds listening to the ceremonies. 



After leaving the amplifier C\ at Arlington, the voice currents first 

 passed through a non-loaded section of cable whose distortion was 

 corrected by equalizer E\. A non-loaded 8-gauge open-wire circuit 

 carried the voice currents to New York City. At this point, the cir- 

 cuit again branched, one branch delivering a part of the voice currents 

 to the apparatus at Madison Square Garden, the other branch going 

 to San Francisco over one of the non-loaded No. 8-gauge transcon- 

 tinental circuits. The arrangements employed at Madison Square 

 Garden and at the Civic Auditorium in San Francisco were similar., 

 switches being provided at each point to connect to the projector 

 groups the circuit from Arlington or from the local transmitter. 



The difficulties involved in transmitting voice currents for the first 

 time to loud speaker installations at distant points, as well as the 

 great importance of the occasion, made it necessary to take elaborate 

 precautions in order to insure the success of the undertaking. The 

 long distance telephone circuits were carefully inspected ahead of 

 time and all of the amplifiers and other apparatus employed were 

 subjected to numerous careful tests. For checking the complete 

 circuit, alternating currents of different frequency were applied at 

 Arlington and measured simultaneously at New York and San Fran- 

 cisco. The curve on Fig. 1 was obtained from the results of one of 

 the measurements made on this occasion. 



To guard against possibility of failure of the circuits, emergency 

 circuits were provided, these emergency circuits taking different 



