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BELL SYSTEM TECHNICAL JOURNAL 



"up" or "down" indication and by adjustments of the repeater or 

 terminal amplifier potentiometers the level may be returned to normal. 

 An alarm circuit is furthermore provided at the receiving terminal 



Figure 7 — Overall transmission characteristics of carrier telephone repeater station 



so that when the level has departed by more than a predetermined 

 amount, say ± 1.5 TU, from the desired normal, the operating at- 

 tendant is called in to make the adjustment. 



A high-frequency current of constant ami)litude is transmitted 



