An audience at a performance

Induction loop systems

This is a simple concept which has been around for a long time.  The audio source could be a microphone, musical instruments or recorded sounds.  These may be going into an audio mixing system and then perhaps to the show relay, but will also be fed to the loop driver which has input processing, amplifies the signal and converts it into an audio current that goes into a loop around the edge of the auditorium.  This current generates a magnetic field of audio frequency in the room which, if correctly designed, will cover every seat.


Ampetronic1Image from Ampetronic

A hearing-aid has a coil inside it that picks up this magnetic field, amplifies it and feeds it out of a speaker in the hearing-aid and into the ear.


  • There’s no need for a receiver, every hearing-aid user brings their receiver with them in the hearing-aid.  Every hearing aid issued by the NHS has a loop receiving facility (or t-switch) which should be matched to the users’ hearing loss and the frequency response of their ear
    • Be warned that sometimes the T-switch / loop reciever has not been enabled by the audiologist
    • Visitors from abroad may have variations on what is familiar in the UK
  • There are no hygiene issues, you don’t have to clean receivers and reissue them
  • There is no discrimination at all to hard of hearing people, if your system is turned on and ready to use, a hearing-aid user doesn’t have to make themselves known or wear anything that identifies them
  • The system doesn’t require much administration.  If it is set up correctly in the first place, you don’t need to manage the issue and return of recievers or do much in day to day upkeep
  • Coverage is not restricted.  Unlike infrared systems, you don’t need to have a clear line of sight between the output and the receiver
  • There is no licensing requirement. Some radio systems have spectrum restrictions concerning where you can put the radio system


Now go to: Standards and requirements