Sadly, not all hearing aids are fitted with the loop facility. In the UK, almost all NHS aids are equipped with a 'T' position, as are many privately sold aids. In the UK private sector, it is often the audiologist who decides whether to offer the loop reception facility, but generally they do offer aids with a 'T' setting. At present, about 95% of hearing aids in the UK are said to have the loop receiving function.
Digital hearing aids work in exactly the same way as ordinary analogue aids in terms of induction loop use but you must make sure that the digital hearing aid has a 'T' switch position. As far as we are aware, all digital hearing aids supplied by the NHS (National Health Service) in the UK have a 'T' coil facility. Privately dispensed digital aids may or may not have a 'T' coil. As policies over 'T' coil provision in hearing aids vary around the world - check with your audiologist about this before you buy, as it may affect what they offer to you. Many digital hearing aids allow the option of setting the relative levels between microphone and 'T' coil inputs to be adjusted by the audiologist. If the loop signal is quiet / loud relative to normal microphone use, ask your audiologist to adjust it for you.