48 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



28 



P4 



(/I 

 O 



_i 



z 

 o 



U1 



z 



20 



12 



10 



20 30 40 50 60 80 100 200 300 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 6 — Transmitting equalizer — loss-frequencj' characteristic. 



of the crystal used in a repeater for performance checking. The gain of 

 a repeater to a signal applied at the resonance frequency of its crystal is 

 about 25 db greater than at 164 kc. 



Deviation Equalizer ■ — • The transmitting deviation equalizer is used to 

 protect the highest level repeater from overload. The design is based on 

 data obtained during the lajdng indicating which repeater was at the 

 highest level at the various frequencies. The characteristic of this equal- 

 izer is shown on Fig. 7. 



A portion of the receiving terminal is shown in block schematic form 

 on Fig. 8. The generalized function of the equalizers is to make the signal 

 level flat versus frequency at the input to the receiving amplifier No. 2. 

 The specific functions of the various equalizers are as follows: 



6 

 4 

 2 

 



20 



40 60 80 100 120 140 



FREQUENCY IN KILOCYCLES PER SECOND 



160 



180 



Fig. 7 — Transmitting deviation equalizer — loss-frequency characteristic. 



