Telecoil

Some articles on telecoil:

Hearing Aid - Technology - Compatibility With Telephones
... signal inside the phone's speaker is picked up by the hearing aid's "telecoil" or "T-coil", a special loop of wire inside the hearing aid ... Note that telecoil coupling has nothing to do with the radio signal in a cellular or cordless phone the audio signal picked up by the telecoil is the weak electromagnetic ... The electromagnetic (telecoil) mode is usually more effective than the acoustic method ...
Audio Induction Loop - History
... The pickup coil in a hearing aid is named Telecoil because its early form was to pick up a magnetic field from coils within a telephone ... The telecoil enabled hearing aid users to hear the phone conversation more clearly without also picking up background noise around them ... natural development was to generate audio magnetic fields which the telecoil could receive ...