Telecoil

The small copper coil inside many hearing aids

Overview

A telecoil, or T coil, is a small coil of copper wire inside many hearing aids and cochlear implant processors that picks up magnetic fields and converts them directly into an audio signal. It was originally designed to pick up the magnetic leakage from telephone receivers, which is where the name comes from. When the telecoil program is selected, manually or automatically, the device can receive sound from hearing loops, loop compatible telephones, and neckloops, bypassing the microphone. Because only the magnetic signal is picked up, background noise and room reverberation are largely excluded. Telecoils are common in behind the ear aids but may be absent from the smallest in the ear designs, and in some devices the program must be activated by the fitter. In the United States, hearing aid compatibility rules for telephones support telecoil use, and the blue ear symbol with a T indicates venues equipped with loops.