must be made with a coil that picks up only the vertical component of the magnetic field, the component that is picked up by the telecoil of a hearing aid. BS 7594 (published by the BSI and widely used in Britain) is a non-mandatory guideline for the design and installation of induction loops. It has a comprehensive guide to theory, as well as guidance for those considering the installation of AFILs in buildings for which they may be responsible. It also contains some valuable guidance relating to other equipment within the loop area. The calibration of field strength measuring devices is also included. References Hearing aids Assistive technology Augmentative and alternative communication fi:Induktiosilmukka