Contact Code 5

Contact Code 5 was a code signal which was part of International Rescue's Emergency Code Machine. To those outside of International Rescue, it simply sounded like a "tapping noise".

History
In an account dated to January 1965, while Lady Penelope Creighton-Ward was kidnapped and could only communicate in secret through a camera connected to Tracy Island, disguised as a makeup mirror, the mirror was slapped to the ground by criminal gang leader Carl. After hearing no sound from the other end, Scott Tracy suggested attempting to contact her, which Jeff warned could put Penelope in mortal danger if the wrong person were to receive the message.

In response, Scott suggested use of the code signal, which would be meaningless to anyone outside of International Rescue. Thus, Jeff used the code signal Contact Code 5 to send a secret message to Penelope. Carl noticed the sound, as well as its sudden stop, which Penelope suggested could have been rats. She proceeded to ask if the rats would be off the boat before it blew up, or if they would go up with it to, secretly alerting her fellow International Rescue members of Carl's plan. (TV: The Man from MI.5)

Other sources dated the activities of International Rescue to the 1990s, (PROSE: The Dying Days) the 2060s, (PROSE: Titan Declares War! et al.) and the 2080s. (PROSE: Captain Scarlet in Death Crash! et al.)