"We follow the scientists around and look over their shoulders. They're watching their feet: provable mistakes are bad for them. We're looking as far ahead as we can, and we don't get penalized for mistakes."
- Larry Niven

The Bellatrix, flashing onward along the flaming corridor of the passage, was still in photophone communication with us. A private call came for Gideon Clew, and Vance, our operator, sent the steward to find the old man.

"A call for me, thir?" he lisped in excited astonishment as he shuffled into the photophone room. It must have been the first in fifty years.

Vance made him sit down in front of the projection screen, and tuned his set and synchronized the scanning tube. The bright-hued geometric figures of the registration pattern vanished suddenly, and on the screen was Tonia Andros.

Vance and the other operator were inevitable eavesdroppers, for without their continual adjustments, the narrow etheric nerve between the ships would have snapped in half a minute.

Again, from Collision Orbit, by Jack Williamson, published by Astounding in 1942:

He reached for the photophone receiver - out along the spatial barriers, where there was no atmosphere to carry sound or to distort and absorb a beam of modulated light, the photophone was almost the universal means of communication, from ship to ship and rock to rock.