CARRIER SYSTEMS ON TELEPHONE LINES 



603 



other than the 15 TU auxihary ampHfier, is identical to the group 

 ampHfiers employed in each terminal station. The filters are also 

 identical in type, excepting that twice as many directional filters are 

 required at each repeater station as at each terminal. 



A typical complete installation of two carrier repeaters with testing 

 and battery supply circuits located in the bay at the left is shown in 

 Figure 24. The bottom panel on the left-hand bay is a reserve 

 amplifier. Above this panel are the filament rheostats, telegraph 

 instruments, jack panels, key panels for controlling the power supply, 

 a panel containing a thermocouple and meter for testing, meters for 

 reading currents and voltages, and finally the alarm relays. These 

 last are operated by failure in the plate current in the amplifier tubes, 

 thereby indicating when a tube burns out, or failure of either A or B 

 battery supply. 



Each repeater bay in this case, Figure 24, contains an auxiliary 

 amplifier to increase the gain in the high-frequency group. From 



Figure 25- 



-Schematic circuit showing line filter equipment for type 

 telephone terminal. (Phantom group) 



'C" carrier 



