Cure Modules

The Cure Module (キュアモジューレ) is a Brooch-like device that allows Kanade and Hibiki to transform into Pretty Cures. The brooch is given to them by Hummy after their first encounter with Mephisto's minions and tells them to transform. To transform, a fairy tone must be inserted in the top slot of the Cure Module before either Kanade and Hibiki says "Let's Play! Pretty Cure Modulation!" and then press the button on the bottom side of the brooch.

Also, other Fairy Tones can be used by the Cure Module to increase a Cure's abilities.

Trivia
The Cure Modules are the second Brooch-Like Items existing in the Pretty Cure Universe. The first being Shiny Luminous' brooch.