Sonic beam

Guerners placed themselves into suspended animation by laying in berths under sonic beams. When the sonic beams were switched off, the Guerners would awaken, not having aged a day, although the process erased their memories. (PROSE: The Sleeping Beast)

In an account dated to January 1965, Brains was performing an experiment in the Tracy Island swimming pool with a model submarine, which used a sonic beam. During this, Jeff warned him that Alan would be out for his swim soon, with Brains claiming that his presence in the water would upset the sonic beam. Shortly after, Alan indeed arrived, throwing off the towel around his neck and jumping into the pool, causing a splash. He proceeded to apologise to Brains for disrupting his experiment. (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.)