Subspace transmitter

From Memory Alpha, the free Star Trek reference.

A subspace transmitter is any mechanism or method that can transmit information through the medium of subspace and thus at a velocity greater than the speed of light.

Starships employ such transmitters to stay in contact with their operational bases, landing parties and away teams. Colonies and civilizations employ them to contact other worlds within the Federation and elsewhere. The Federation maintains a network of subspace relays that are essentially repeaters; these enable even distant transmitters to reach any point within Federation space.

The subspace transmitter aboard the Arcos was failing when it was orbiting Turkana IV in early 2367 meaning that the distress call sent by the ship was very weak and distorted although the USS Enterprise-D, the ship that received the message, was only eleven minutes away from the Turkana system. (TNG: "Legacy")

Subspace communication
amplifier • antenna • bandwidth • beacon • hyper- • interference • interplexing beacon • log • message • neural transceiver • oscillation • relay • relay network • relay station • transceiver • transmitter • transponder • wide-band