Inductive coil used in some hearing aids to allow reception of an audio band magnetic field signal instead of an acoustic signal. The magnetic or inductive mode of reception is commonly used in conjunction with telephones, auditorium loop systems, and other systems that provide the required magnetic field output.

Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST), https://pages.nist.gov/ElectionGlossary/; Glossary of terms database, U.S. Election Assistance Commission, https://www.eac.gov/glossary/