A hearing loop (sometimes called an audio induction loop) is a special type of sound system used to make it easier for people with hearing aids to hear. A loop system is particularly useful in busy or loud environments. The hearing loop provides a magnetic, wireless signal that is picked up by the hearing aid when it is set to ‘T’ (Telecoil) setting.
The hearing loop consists of a microphone to pick up the spoken word; an amplifier which processes the signal which is then sent through the final piece; the loop cable, a wire placed around the perimeter of a specific area i.e. a meeting room, a church, a service counter etc to act as an antenna that radiates the magnetic signal to the hearing aid.
Please click on the link that follows to be taken to a fuller description of a loop system and what it is and how it works this will open in a new tab. (with thanks to Hearing link) https://www.hearinglink.org/living/loops-equipment/hearing-loops/what-is-a-hearing-loop/