TYPE-0 CAIIRIEH SYSTEM 



697 



TJne filters (G) are provided to separate the OB, OC, and OD Systems 

 from (he OA freciueiicy i-anges. Because of the lower attemiation and 

 slope in the OA frequency range, and the ])etter line coupling factors, 

 the repeaters do not "frog" the high and low groups. 



The OB Carrier Terminal 



A block diagram of a typical carrier terminal is shown on Fig. 7, 

 in this case the OB terminal. The terminal is comprised of four channel 

 units, two twin-channel units, group transmitting and receiving units, 

 and a group oscillator. An oscillator in each of the twin channel units 

 .supplies carrier to the transmitting channel modulators. The same oscil- 

 lator supplies transmitted carrier for two associated sidebands. The 

 original carrier is balanced out in the transmitting modulator. This 

 nie^hod results in a more accurate control of the transmitted carrier. 

 le\el. The group oscillators supply the necessary frequencies to the 



Table I 



* Except OA sj^stem. t Cut-apart region between 36 and 40 kc. t Cut-apart 

 region between 30 and 40 kc. 538A is a 537A filter with housing and protectors 

 for pole mounting. 



