The RCA Selectron -- US Patent 2,442,985 Selectron Optical Readout

Jan A. Rajchman, Radio Corporation of America
Applied: 08 January, 1947
Granted: 08 June, 1948

Schematic of photoelectric readout circuitry and mechanical diagram of Selectron, parabolic mirror and phototube The '985 patent covers the an all optical readout system for Selectrons. Reading the miniscule currents of the electrical output of a Selectron was non-trivial. The high voltage (and current) switching signals would easily overwhelm the output. The optical readout of the Selectron gave a way to easily detect the presence or absence of a bit. A photomultiplier tube would detect the presence or absence of light when a single bit was interrogated. Optical shielding is easy: steel and black paint.

US Patent 2,442,985 (OCR'd) 100 kB
US Patent 2,442,985 (OCR'd) 100 kB