AN IMPROVED THREE-CHANNEL CARRIER TELEPHONE SYSTEM 65 



TELECHRON Q, ^ 



MOTOR 3 (O) 



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Fig. 12 — Regulator circuit. 



in an alarm circuit described later. With normal current flowing, 

 corresponding to the proper pilot level at the output of the amplifier, 

 the pointers of these relays are on midscale with a reading of db. 

 When the pilot level changes by more than .5 db in either direction, 

 contacts close on the relay controlling the regulator and cause power 

 to be supplied to a Telechron motor which controls the continuously 

 variable artificial line mentioned above. This will be driven inter- 

 mittently at a rate of about 1 db per minute until the output level 

 has been restored to within ± .5 db. 



As will be seen from the sketch the variable line consists of three 

 sections connected in tandem. The ends of these sections are con- 

 nected to the four stators of a variable air condenser. The rotor of 



