This NORDTEST method applies to complete audio induction loop systems for hearing aid purposes, permanently installed in rooms and consisting of signal sources (e.g. microphones), amplifiers and induction loops. Parts of the method described may, where relevant, also apply to other induction loop systems.
Mostly however, induction loop systems form an integral part of a public address sound system, using separate power amplifiers for the induction loops. However, small induction loops are sometimes connected in parallel to the loudspeaker terminals of the sound system (loudspeaker-dependent induction loop), in which case it must be realized that the setting of gain and tone controls will be in accordance with the requirements of the loudspeaker system rather than in accordance with the induction loop system.
The test method is restricted to a description of certain characteristics and the relevant method of measurement for induction loop systems; it does not attempt to specify performance requirements.