A CARRIER TELEPHONE SYSTEM FOR TOLL CABLES 



95 



accurate indication of the temperature of the carrier pairs which 

 determines their attenuation to a close approximation. The motion of 

 the bridge mechanism is communicated to the repeater ampUfiers by 

 means of self-synchronizing motors, a master motor being associated 

 with the bridge and an individual motor with each amplifier. 



With aerial cable a flat gain correction must be made at every 

 repeater. With underground cable the flat gain correction may be 



-3 



-5 



5 10 15 20 25 30 35 40 45 50 55 60 65 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 14 — Characteristics of twist regulator networks. 



omitted at some repeater points. Figure 13 show^s a master controller 

 with its galvanometer, driving motor, and self-synchronizing motor. 

 The air condenser in the feedback circuit of Fig. 8 makes this cor- 

 rection. The small self-synchronizing motor which may be seen in 

 this figure is geared to the condenser and it moves the air condenser 

 corresponding to the motion of the master motor. The resulting 

 change in repeater gain is virtually the same for all frequencies in the 

 transmitted band. In Fig. 10 the repeater gain is plotted against 

 frequency for three angular positions of the condenser. 



