PUBLIC ADDRESS SYSTEMS 



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now be described. In order to make clear the arrangement of the 

 equipment, a typical installation is shown in Fig. 4, this being an 

 installation where the audience and speaker are in the open air, and 

 where no connection is made with the long distance lines. It might 

 be well to state here that with the equipment shown an audience of 

 700,000 can be adequately covered. 



Some of the sound leaving the speaker's mouth is picked up by the 

 transmitter, on a reading-desk type of pedestal, which is normally 

 mounted at the front of the platform. 



The feeble currents from the transmitter are led by carefully 

 shielded leads to the amplifiers in the control room, which is usually 



Fig. 5. 



located directly beneath or to one side of the speaker's stand. A 

 floor space of not more than 125 square feet is required for this room, 

 even in the case where it is desirable to transmit phonograph music 

 to the audience between speeches. 



The amplifier and power supply equipment is shown on the two 

 panels in the center of the control room. The amplified speech cur- 

 rents are led from these amplifiers to the receiver projector units, 

 which, in this case, are arranged on the super-structure above the 



