PULSE MODULATOR TUBES 



825 



conductivity material. Both grids were gold plated as in the 701A. All 

 electrodes were mounted between two specially shaped ceramic insulators 

 which provided a relatively long path between plate and grids. This 

 structure is shown in Fig. 5. Heat radiating fins were attached to the ends 



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Fig. 5 — The 7 15 A vacuum tube. 



of the control-grid and screen-grid supports. The plate is molybdenum 

 with zirconium coating on its outside surface. This coating was employed 

 to increase the thermal emissivity of the plate in the interest of a low operat- 

 ing temperature. It also serves to absorb some gas. The cathode, heater 

 and grid terminals of the tube were brought out in the moulded-glass 4-Pin 



