Covariant isolator
A covariant isolator was a piece of technology on  vessels, used to clear up garbled subspace messages.

In 2371, while trying to contact Telek R'Mor through the Harry Kim wormhole,  B'Elanna Torres was concerned that the covariant isolator would not be able to penetrate the unusual phase variance in the wormhole to hear his message. However, the crew of the  was able to establish contact with R'Mor by narrowing the filter band pass. ()

de: Kovarianter Isolator
Communications technology