Myriad
Subspace communication using Myriad
Myriad was an encryption codec for subspace transmissions, developed in the mid-24th century by USS Enterprise-D personnel during a mission to Rigel VII, when they thought their communicators had been compromised.
In 2401, Doctor Beverly Crusher sent a distress call to Admiral Jean-Luc Picard using the Myriad codec, which directed the message to his old combadge from the Enterprise-D. (PIC: "The Next Generation")
It would later be used by President of the United Federation of Planets, Anton Chekov, when broadcasting the emergency transmission during the Battle of Frontier Day. (PIC: "The Last Generation")