Unlike most other fiction, in the world of Toaru Majutsu no Index, telepathy makes use of an invisible "wire" made by the user through the manipulation of the vibration of air to create a frequency. It is like an acoustic tube, able to pass the vibrations created by the sound, and passing it to through a connected circuit. Apparently, any part of the body would do to make a connection, and apparently, the higher the level, the more wires can be constructed. The sound is sent directly to the brain afterwards.
Apparently, telepathy is one of the many information transfer abilities. Other than sound, a skilled telepath can determine the general location of a person they are connected to, like a GPS. 
If the Imagine Breaker happens to pass through the wire, then the connection is severed. Furthermore, those who are connected are unable to lower the volume of the "sound" being transferred, as the telepath controls it. There is also a limit to the length of the wire that is created depending on level, as someone can escape the telepath's range.
- Shokuhou Misaki - Level 5 Mental Out
- Yotsuba - Level 4
- Unnamed Judgment member - Level Unknown
- Haruue Erii - Level 2
- Edasaki Banri - Level Unknown
- Futaishi Kyousha - Level 2
- Kobayashi Satori - Level 3
- Mitsuari Ayu - Level 3 Mental Stinger