A subspace relay is a device that facilitates superluminal communication across subspace. Relays are commonly used in starships, by phone companies, and in other facilities that feature in long-distance communication.

For reasons unknown, signals can be sent across no more than 50,000 light years of distance (often called the "50k Barrier"). There are many stations near the core of the galaxy that specialize in receiving and retransmitting subspace signals for the sake of cross-galaxy communications.