A communicator was a hand-held device used by many species for person-to-person, person-to-ship, inter-ship communications, usually transmitting on subspace frequencies. They were used by Starfleet landing parties and away teams, and occasionally they were used in situations where normal intra-ship communications were inaccessible or inadvisable, during the 22nd and 23rd centuries. Employing a flip-top design, a member of Starfleet spoke directly into the device to give commands and speak with other personnel.
In some cases, communicators served purposes beyond basic communication. By 2152, the power signature of a Starfleet communicator could be amplified by an inverse carrier wave, making the communicator detectable by sensors. For another example, when accessing a computer, the communicator of the person at the terminal logged in the user information, thereby making it possible to trace back who accessed the computer. Communicators were also often used to allow transporter locks for beaming, thus acting as homing transponders. When used in tandem, two communicators could produce a sonic disruption by using sound beams to create a sympathetic vibration in an unstable object, such as a cliff face. Usage of a communicator, while receiving and outputting a signal, could be hidden from sensors by triaxilating the signal.
By the 24th century, these communication devices were integrated into the standard uniform badges and became known as combadges. Users no longer had to speak directly into the communicator, but rather could activate and deactivate them with the touch of a finger.