Visual circuit

A visual circuit, or vision circuit, was, broadly speaking, a technological component which allowed for vision.

In the 40th century, the android Mark Seven was equipped with a vision circuit which was infraspectrum sensitive. (AUDIO: The Destroyers)

A grey Dalek used a visual circuit as means of sight. During the Dalek-Movellan War, the Fourth Doctor used his hat to block such a Dalek's eyestalk, impairing its visual circuit. (TV: Destiny of the Daleks)

A different visual circuit was used as a monitor in the office of Tobias Vaughn at International Electromatics. (TV: The Invasion)