754 



BELL SYSTEM TECUNTCAL JOURNAL 



restore the grid circuit to reference zero potential. This particular d-c 

 restorer circuit form is referred to as a positive restorer, indicative of the 

 final polarity of the restored signal. A simj)le reversal of the diode elements 

 will reverse the polarity of the restored signal. 



Figure 34b illustrates the usual radar circuit form of a negative d-c 

 restorer, where the diode is eliminated, the normal vacuum tube grid circuit 



Fig. 34. — Typical D-c Restorer Circuit Forms. Simplified schematic diagrams. 



serving here to fulfill this function. Here again an impressed signal form 

 having an average value of zero is assumed, and a negative polarity re- 

 stored signal is desired at the grid of the amplitier tube. During periods 

 of positive excursions of the input signal the vacuum tube grid will conduct 

 since it is normally operated at zero bias. The series condenser C is ac- 

 cordingly charged relative to the positive signal peak amplitude and this 

 value of potential will be additively combined with the signal during nega- 

 tive excursions in a similar manner to the diode restorer action just de- 

 scribed. 



.A. third form of d-c restoration is known as a clamper or synchronized 

 d-c restorer and is illustrated in Fig. 34c. Here a diode bridge circuit 



