Combadge

A Combadge is a small personnel communications device integrated into badge worn by Starfleet personnel in the 24th century and beyond.

Combadges are used for communications from individuals to other persons, starships, planetary locations and anywhere else within the range of the device. They also function as a locator device for transporter beams and have integrated universal translators. (VOY episode: ''The 37's, et al.)

In 2364 Tasha Yar modified her combadge to output a high pitched whine, sufficiently distracting and pain inducing to allow her and Commander Riker to fight their way past numerous guards on the planet Tigan. (TNG comic: History Lesson)