The test instrument
A testing device should always be available where a loop is installed. The person who is responsible for the venue can with a quick and simple check make sure that the system is operational. A yellow or green LED will indicate if the loop works properly. Green indicates that the loop fulfills the international standard IEC 60118-4 level requirement. A yellow LED indicates that the loop is operational but does not meet the IEC level requirement, but will still benefit the user. You may also listen to the loop system through the speaker or earphones that connects to the instrument’s 3.5mm output. Loop Listener gives a calibrated field strength measurement for speech according to IEC 60118-4 (125 msec, rms). Some high crest music material may give 1-2dB increased value.