The codec system debuted in the Metal Gear series and became iconic with Metal Gear Solid on PlayStation in 1998, where Solid Snake received mission briefings from his support team by radio. Its two-tone call signal was designed to be heard instantly over gameplay, and it returned in sequels, remakes and spin-offs for decades. As gameplay clips and fan edits spread online, the beep escaped the games and became shorthand for a covert incoming call, which is why it remains popular as a ringtone and meme cue.