SYSTEM ADAPTATION 



307 



mounted in a cabinet (Fig. 6) at the right side of the director's position. 

 Continuously variable volume controls for the three channels were 

 mounted on a common shaft and housed in the center cabinet of Fig. 6. 



20 50 100 500 1000 5000 10,000 20,000 



FREQUENCY IN CYCLES PER SECOND 



Fig. 5 — Transmission characteristics of quality control networks used in the Phila- 

 delphia-Washington experiment. 



A separate control for the center channel was provided when that was 

 used for the soloist. In addition to the high quality channels certain 

 auxiliary circuits were supplied to aid the smoothness of performance. 

 Supplementing the order wire connecting all technical operators, a 

 monitor circuit was provided in the reverse direction. The microphone 

 was located on the cabinet before the director, and loud speakers were 

 connected in the control rooms and on the stage with the orchestra, 

 enabling the control operator to hear what went on in the auditorium 

 and allowing the director to speak to the orchestra. Two useful 

 signal circuits were employed; one giving the orchestra a "play" or 

 "listen" signal, and at the same time connecting either the auditorium 

 or the orchestra's loud speakers, respectively; the other being a 



Fig. 6 — Cabinets housing quality control networks and providing communication 



facilities for operation. 



