Linguacode was a translation matrix used during first contact scenarios, often employed when the universal translator was unable to facilitate communication. The language was developed by noted communications officer Hoshi Sato in the 2160s. (ENT: "In a Mirror, Darkly, Part II") It was generally regarded as a mode of communication that any lifeform capable of warp travel should be capable of deciphering. (Star Trek: The Motion Picture)
In the 2270s, the Epsilon IX station transmitted linguacode friendship messages as the V'ger cloud approached, but received no response. The station was subsequently absorbed by the cloud and destroyed. As the USS Enterprise intercepted the cloud, Captain Kirk ordered Communications Officer Uhura to broadcast greetings in Linguacode; again, V'ger was unresponsive. The giant cloud then opened fire on Enterprise. Science Officer Spock concluded that V'ger was unable to receive their "primitive" form of communication, which was too slow to be received. Spock adjusted their linguacode transmission to a frequency of more than one million megahertz, allowing V'ger to receive and understand their messages of friendship. V'ger then ceased its attack. (Star Trek: The Motion Picture)
In 2366, Tam Elbrun suggested that linguacode was insufficient to communicate with the space-going lifeform Gomtuu. Elbrun believed that only "direct mind-to-mind" telepathic contact would suffice. A D'deridex-class warbird hailed Gomtuu with what Lieutenant commander Data described as the Romulan version of linguacode, but the Romulans received no response from the lifeform. (TNG: "Tin Man")
Sato's development of the matrix is covered in the Enterprise novel Rosetta.
In the The Sky's the Limit short story "Friends With The Sparrows", Sato's breakthrough is referenced as "Sato with the Antianna" by Data when his emotion chip is modified to allow him to think and speak metaphorically in the same way that the Tamarian language is expressed.