PROGRAM TRANSMISSION CIRCUITS 



239 



' everiag without once changing the tuning, it will be apparent that minute- 

 to-minute rearrangements of an established interconnecting network must 

 ; be possible. For example, studios have to be changed from receiving to 

 ' originating, sections of the network have to be made to transmit first in 



COLUMBUS -DAYTON SECTION 



1927 28 29 30 31 32 33 34 35 35 37 38 39 40 



YEAR 



Fig. 3 — Variations in full-time program circuits 



one direction and then in the other, and branches have to be connected and 

 disconnected. These changes in the network have to be made in the few 

 seconds elapsing between the close of one program and the start of the next 

 on the receipt of selected cue words or sounds. Even during the course of a 



