He passed his hand rapidly over the photoelectric eye of the commo box.
"Null-ABC"
Henry Beam Piper and John Joseph McGuire
P. Penjal traps, 135. Pepys and skating, 273. Perry, coefficient of friction of greased surfaces, 265. Phobos, dimensions of, 177; orbit of, 177. photoelectric activity and absorption, 207; persists at low temperatures, 208, 209; not affected by solution, 213. Photo-electric experiment, 205; sensitiveness of the hands, 207; theory of latent image, 204, 209 et seq.
"The Birth-Time of the World and Other Scientific Essays"
J. (John) Joly
There's a screen of photoelectric cells behind the right eye, so connected that when a certain pattern is thrown on them, it activates the mechanism.
"The Ideal"
Stanley Grauman Weinbaum