Slipbeacon

The Slipbeacon is a supposedly faster-than-light emergency signal device used by the UNSC. Compact enough to be mounted on a starship, the Slipbeacon is known to be used in distress situations. Beside messages carried by starships in shipboard memory or Slipspace COM Launchers, it is the one of the few methods of faster-than-light communication known to the UNSC, though its exact nature or function is unclear.

A distress Slipbeacon to FLEETCOM was raised by Team Black shortly after their ship crash-landed on an unnamed Moon.

Trivia

 * When the rear half of the was left stranded in space after the Battle of Installation 00 with John-117 and Cortana onboard, Cortana mentioned that she would "drop a beacon" in hopes of a rescue party. Given the circumstances, this may well be referring to a Slipbeacon.