SYNCHRONIZATION OF TELEVISION 



615 



employing a sharply tuned circuit as the primary speed-controlling 

 element resonating at a frequency slightly less than the frequency at 

 which the machine is operated. A voltage from the high frequency 

 generator is applied to this tuned circuit and thence to a detector 

 tube which in turn operates on the grids of a pair of push-pull regulator 

 tubes; these tubes controlling an auxiliary regulating field winding 

 on the motor. The circuit also contains anti-hunting means, the 



110 VOLTS 



Q DC 9+ 



Hh 



X 



TO REGULATING 

 riELD OF MOTOR 



Fig. 10 — Speed regulator 



theory of which will be given in the later paper. Instead of applying 

 this regulating circuit to the small 15-in. scanning disk motor shown 

 in Fig. 3, it was decided on account of its greater flywheel effect to 

 use the large 36-in. disk shown in Fig. 5 which was used for receiving 

 the picture at New York. It therefore became the transmitter from 

 the synchronizing standpoint for all of the other units although from 

 the picture standpoint the big disk acted as a receiver. 



Local Stations 



In addition to the stations at Washington and Whippany there 

 were three local stations in New York employing similar high and 

 low frequency synchronous motors with 15-in. disks. These were 

 controlled in the same manner except that first stage of amplification 

 and the line filters were omitted. One station was employed for 

 monitoring purposes, another operated a local transmitter, while the 

 third operated the big grid receiver seen by the entire audience. 



40 



