/ˌfoʊtoʊˈfoʊn/ (FOH-toh-fohn)

Definitions

1. noun

an early device for transmitting sound over wires by converting sound into light, which was then converted back into sound at the receiving end.

“In the late 19th century, the inventors developed an early version of the photophone.”

2. noun

an early device for transmitting speech over wires by converting sound into light and vice versa.

“The scientists created a working model of the photophone using a beam of light and a sensitive receiver.”