Doctor Noel attempts to deactivate the hyperpower circuits at the Tantalus V penal colony.
Hyperpower circuits were an energy-generation technology utilizing megavoltage, used to power large installations or facilities.
The Tantalus V penal colony utilized hyperpower circuits. In 2266, Doctor Helen Noel was successful in powering down the circuits in order to deactivate the security screen surrounding the colony, allowing Mister Spock and a security team to beam down and take Doctor Tristan Adams into custody, as he had become dangerously unstable. (TOS: "Dagger of the Mind")