Star Trek: 10 Things You Didn't Know About Combadges

Combadges transmitted using subspace frequencies, the same technology that allows for faster-than-light communication between starships. Because of this, if Starfleet officers ever got lost or stranded alone, it was actually possible for them to modify their combadge into a subspace distress beacon.

The range of these beacons was very limited compared to a dedicated subspace transmitter, but any ship passing by close to a planet would be able to detect the signal from the surface and conduct a rescue operation. This function has probably saved countless lives in Trek, as almost every officer stranded on an alien planet would still have their combadge on them.

We also know that an emergency distress signal would be activated from the badges if their outer casing was ever damaged, either to let the officer's ship know that they are in danger or to help the crew locate fallen officers.