"The 2E22 is a directly heater pentode for RF power applications. It looks similar to the indirectly heated 807 but operates at higher voltages and produces more power. The ceramic insulators indicate the high anode voltages involved. The directly heated cathode avoids problems with heater/cathode shorts.

The suppressor grid has its own pin and can be used for modulation input. The 807 has g3 tied internally to the cathode."