Rooms with no metal structures present, up to 25m wide. Rooms with metal structures present up to 4m wide, or as little as 2m wide for severe metal losses. Rooms where overspill is not a problem, i.e. where there are no nearby or adjacent induction loop systems, and where confidentiality is not important.
Single loop of cable or foil around the perimeter of the area to be used, driven by a single loop amplifier system.
Large loops cause variation over the width of the room. Very large rooms (>25m with no metal) will have a much lower signal at the centre than the outside. Where metal structures are present, metal losses will dramatically reduce the field strength towards the middle of the loop. With metal present, perimeter loops are only of use in small rooms.