It is possible that these rings were based off the rocks that were used by the original Pokémon before the great war to become human to guide the homo sapiens.
These rings are exclusively used by PRT members past the STAR rank or by Pokéumans who have defeated the Elite Four of the base. 1st class PRT members are allowed to use prototype rings. These rings time out automatically after 30 minutes.
Special rocks have been discovered that, when used in a humanizing ring, can make the ring wearable indefinitely without causing mutation. However, very few samples of these rocks have been found, and they are not available for use in most circumstances. One of the few instances of such rocks being used in a story appeared in Rescue Number 301.