The combadge, also spelled commbadge, is a combination insignia and communicator worn on Starfleet uniforms. Several designs have been issued; the first was in service by the 2340s. By the late 24th century, they also included universal translators. Transporters and sensors would lock onto an officer by signals emitted from the transceiver in their combadge. (TNG: "Yesterday's Enterprise"; DS9: "For the Uniform"; VOY: "The 37's", "Investigations")
Upon resignation or relief of duty, Starfleet personnel must relinquish their combadges. Sudden resignations often involve the removal of the combadge as a symbolic act. (TNG: "Redemption"; DS9: "Paradise Lost", "Tacking Into the Wind", "Inter Arma Enim Silent Leges")
By 2379, an upgraded version of the combadge was being field tested on board the USS Prometheus at the request of the Starfleet Corps of Engineers. This version of the combadge contained a dual interplexed subspace transceivers, a secondary power cell, an interface module to allow it to work in concert with a Feinberg Reciever, and a perscan module. Outwardly this combadge appeared as a silver Starfleet delta insignia without a background.