Ernst Ruhmer (nonfiction)

Ruhmer listening at one station to his "photo-electric" optical telephone system (1905).

Ernst Walter Ruhmer (15 April 1878 — 8 April 1913) was a German physicist. He was best known for investigating practical applications making use of the light-sensitivity properties of selenium, which he employed in developing wireless telephony using line-of-sight optical transmissions, sound-on-film audio recording, and television transmissions over wires.