TYPE-0 CARRIER SYSTEM 



703 



filter is reversible as well as plug-in and thus serves either high or low 

 groups. The receiving group band filter and its associated auxiliary filter 

 have the same physical arrangement as in the repeater but they are 

 never reversed. 



A dc feedback type regulator controls the gain of the regulating ampli- 

 fier, and operates principally on the two received carriers, although the 

 sidebands are fed back also. 



Group Oscillator 



The group oscillator contains two oscillators for supplying the group 

 transmitting and group receiving units. These oscillators are interchange- 

 able (by strapping) and permit the group units to operate in either the 

 high or low groups. For conveneince the 3700 cycle signaling oscillator, 

 common to all four channels, is contained in the group oscillator. 



Repeater 



As indicated on Figs. 5 and 6, a repeater is pro\dded for each four- 

 channel system. An amplifier, regulator and modulator arrangement 

 serves each direction. The directional bands are routed through the 

 repeater by directional and auxiliary band pass filters as indicated on 

 Figs. 13 and 14. At each repeater (except OA) the high- and low-fre- 

 quency groups are "frogged" to improve transmission, particularly as 



FROM 

 CHANNEL <^ 

 UNITS 



FROM 

 TWIN- 

 CHANNEL 

 UNITS 



COMB MULT 



■ \Vv 





\AyV 



MODULATOR 



TRANS GROUP 

 LPF 



E 



NOISE 

 GENERATOR 



TO GROUP 

 I REC UNIT 







3700 

 CYCLES 



TO GROUP 

 REC UNIT 



1 



THROUGH DIR 



FILTER IN GROUP 



REC UNIT 



40-56KC 



(OR 60-76 KC) 



TO KEYING 

 CIRCUITS 



Fig. 11 — Tjpe-OB group transmitting unit and group oscillator unit. 



