Opto-aud

From Memory Alpha, the free Star Trek reference

The opto-aud was used by Theela on Taurus II to find suitable men from whom to drain their vital energy.

The opto-aud was a very advanced device. It could display images and information from people and/or ships at distances as far as 20 light years. It was activated by tonal control and revealed anything that it was asked. (TAS: "The Lorelei Signal")