Rho waves, also called rho patterns (GAME: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"}) or rho fields, (GAME: "General Adventure Procedures" [+]Part of The Legions of Death, Loading...{"namedpart":"General Adventure Procedures","1":"The Legions of Death (game)"}) were waves "intangible mental signals unique to all living and semi-living things". Analysis and processing of a thinking being's rho waves could allow for modifications, enabling induced hallucinations, personality changes, and hypnotic control.
Rho waves could be emitted by artificial rho wave field projectors, or simply rho wave projectors. (GAME: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"})
History
The Time Lords discovered rh waves "in connection with experiments in telepathy and hypnosis", soon discovering that rho waves could disrupt TARDISes and thus strongly cautioning careless Time Lords against the use of rho wave projectors. However, a less invasive for of the technology was incorporated into the design of the Model 65 TARDISes' infamous SID security system, which scanned personnel's "characteristic rho patterns" along with their retinal prints to compare them to "an 'approved entrance' file". (GAME: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"})
The hypnotic processing machines used by the War Lords in the War Gamess (TV: The War Games [+]Loading...["The War Games (TV story)"]) manipulated "rho patterns in the subject's brain", rendering them "extremely susceptible to suggestion, perceiving [their] surroundings as [they] were ordered to do". However, after processing, there was a distinct chance that the programming would wear off over time. (GAME: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"}) After the Second Doctor alerted the Time Lords to the War Games plot, (TV: The War Games [+]Loading...["The War Games (TV story)"]) Time Lord scientists studied the machines; they theorised that the machines' efficacy could be improved if complemented by "a device that would support initial processing with continued rho wave transmissions to constantly reinforce the original effects".
While the War Lords had only dabbled in such experiments when they were stopped, (GAME: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"}) a regenerated War Chief put this theory into practice with some processing machines he'd salvaged, (GAME: "Special Equipment" [+]Part of The Legions of Death, Loading...{"namedpart":"Special Equipment","1":"The Legions of Death (game)"}) linking them to relays he mounted inside refitted Sontaran recon drones, which were akin to (GAME: "Shadows in the Night" [+]Part of The Legions of Death, Loading...{"namedep":"Shadows in the Night","1":"The Legions of Death (game)"}) the hypnosound devices later used by the Master during the Human-Draconian War. (PROSE: "Player's Handout" [+]Part of The Legions of Death, Loading...{"namedpart":"Player's Handout","1":"The Legions of Death (game)"}, TV: Frontier in Space [+]Loading...["Frontier in Space (TV story)"]) His meddling in 43 AD Britain was discovered after the Celestial Intervention Agency detected the energy signature emitted through the Time Vortex by his TARDIS as it continually drew power to sustain the operation of the machines and the relays' control centre. After the Time Lord or Time Lords dispatched to 1st century Britain learned the truth about the War Chief's plan, they destroyed the processing machines and control centre. (GAME: The Legions of Death [+]Loading...["The Legions of Death (game)"])