Permanent, professionally installed units, such as service counters at checkout counters, information desks, ticket windows, etc. provide a calibrated hearing loop that meets IEC standards, proper placement for users who both stand and use wheelchairs, correct microphone selection and placement (sometimes affixed), and continuous power. There are different types of aerials and area coverage can vary. When possible the sign should be fitted at the exact position of the loop antenna. This gives consistency and reliability for all users: immediate availability without requesting and the unit will always work well.
There are 4 types of permanent counter hearing loops
Portable units are good for one-time or on-the-fly needs, such as for small meetings, but have their limitations. In general, they have a small field, which means orientation, microphones selection, and placement are important.