AN IMPROVED THREE-CHANNEL CARRIER TELEPHONE SYSTEM 67 



There should be added to the comparison the fact that the new 

 ampUfier does not require selection of tubes to obtain satisfactory 

 modulation results. It is also more stable with variations of power 

 voltages and changes of vacuum tubes. The large space saving will 

 be evident from Fig. 13, which pictures the new amplifier with the 

 old push-pull amplifier and its auxiliary. 



301" 



Fig. 13 — New amplifier compared with the older t)pe which it replaces. 



The circuit of the amplifier is shown in Fig. 14. It is a two-stage 

 circuit using pentode tubes. As will be seen from the circuit the 

 feedback connection is obtained through the use of input and output 

 transformers which are essentially hybrid coils. These coils are 



