The 20CV photocell has a B8G base but only four pins are present. The construction is an early form of the pressed glass disc to hold the electrodes. The pins are extensions of the electrode supports. The pressed glass foot was first used by RCA in 1935 for their metal valves.

The semi-circular photocathode would release electrons in proportion to the light intensity reaching the cathode. The rod anode would be held at about 90 Volts positive of the cathode to collect the photoelectrons.

The wide glass tube envelope is 29 mm in diameter and, excluding the B8B base pins, is 62 mm tall.

This exhibit was last updated on 02 December 2007