19S 



BEI.I. SYSTEM TECIIXICAI. JOl'RXAL 



III l"i^. 11 i> >li()\\n (at the to])) a diagram of ilic liirici currfiu 

 aini)litier and the modulator used for the picture cliamiel, together 

 with diagrams (at the bottom) showing the electrical characteristics 

 of each element of the system. Starting at the extreme left is the 



Fig. 11 — Circuit schematic of aiiiplifiiT-modul.ilor with characteristics of 

 each clenifnt 



photoelectric cell, the current from which passes ihr(iui;li a liii;!) 

 resistance. The potential tapped off this resistance (of ilie order of 

 'M) or 40 millivolts) is applied to the grid of the first \acuum ttihe 

 amplifier. The second vacuum tube amplifier is similarly cotijiled 



