TUBE FOR PULSE CODE MODULATION 



53 



at the left hand side of the aperture plate in Fig. 5 provide a peak amplitude 

 range for which the output pulse group consists of all seven pulses. This in 

 effect provides a peak limiting action. 



Leads from the four electrodes of the target assembly are brought out 

 directly to terminal caps on the side and end of the tube envelope to decrease 

 the interelectrode capacitances and to facilitate direct connection to external 

 circuits. 



Fig. 6 — Quantizing grid. 



Operational and Design Considerations 



The quantizing action depends on the periodic variation of electron beam 

 current intercepted by the wires of the quantizing grid with beam position. 

 Secondary electron emission from the grid and other electrodes was assimied 

 to be negligible with the feedback circuit connected directly to the quantiz- 

 ing grid as shown in Fig. 2. The uniform suppression of secondary electrons 

 is difficult to achieve even though the grid is coated and processed for a low 

 secondary ratio. It is also difficult to prevent secondary electrons produced 

 at the aperture plate from being collected by the grid. 



A preferred method of operation utilizes the secondary electrons produced 



