The P535/1E is a tetrode pulse modulator intended to be driven by a rectangular pulse. The peak current demands require four independent cathodes and the warm-up time should be three minutes if full current is to be drawn. The peak pulse power is 225 kW and the anode has a 60 Watt dissipation.
We also have the higher voltage P552/1E high vacuum pulse modulator.
High voltages necessitate good insulators and the insulator of choice is ceramic.
The gold plated grid wires. The control grid is topped with radiating fins. The grid wires are substantial for both mechanical strength and for peak current handling.
The lower ceramic insulator and the four cathodes. Note that the control grid has heat radiating fins on the lower ends of the supports as well as at the top and that the screen grid also has fins.
The wide glass tube envelope is 64 mm in diameter, and excluding the B4A base pins is 136 mm tall.
Reference: Datasheet. Type P535/1E was first introduced in 1946.