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BELL SYSTEM TECHNICAL JOURNAL 



meter panel for observing the voltages and currents of all the items of 

 equipment which do not have individual meters associated with them. 



Observing System 



In addition co the monitoring projector provided in the control 

 room for the guidance of the operator, it has been found necessary in 

 all but the simplest installations to provide observing stations at 



Fig. 15. 



various points in the audience. The observers stationed at these 

 points are equipped with portable telephone sets, by which they may 

 immediately communicate with the operator, who is provided with a 

 telephone set consisting of a head receiver and a breast transmitter. 

 The value of these observation stations for regulation of output 

 volume during a program will be apparent. 



In the case of an open air performance a variable wind may make 

 it necessary to increase the volume of certain projectors and decrease 

 the volume of others in ordei to cover the audience uniformly. With- 

 out the observers, the control operator would be unable to take care 

 of these changes. 



Considerable preparation is required where the equipment is being 

 used for the first time, in order that the performance of the public 



