There are many ways to use the phone with hearing aids. The basic
and straight forward solution for talking over the phone while using
hearing aids is the T-coil. That’s the T-coil’s original purpose, and
this is the classic solution. Nowadays they use lots of other ways to
connect your phone to your hearing aid.
The original solution was simply using the phone magnetic signal. Once you put the hearing aid in ‘T-coil mode’, the T-coil inside the hearing aid receives this magnetic signal. The T-coil actually replaces the hearing aid’s microphone in this case. Instead of microphone receiving sounds, (the basic function), the T-coil receives the magnetic signals.
Today, you can use the T-coil in other ways too. For instance, you can get an accessory that you place behind your ear, and you plug it to the phone on the other end of the cord. The part behind the ear transmits to the T-coil the signals from the phone. Here is an example of such a device.
Nowadays, many companies offer a unique intermediate device that you connect to the phone in some manner (cable, or Bluetooth). This device sends the sounds from the phone to your hearing aid. This too, can be done in many ways, using the T-coil and a neck-loop or some radio frequency protocol the company may use.
Typically, every hearing aid company got its own phone accessory.
Here is the link to Starkey solution for phones & hearing aids.
You can also find accessories that can work with most hearing aids
and that are not unique to a certain brand. Some of the solutions are
not wireless, of course. As I mentioned above, some of these
accessories use T-coil mode.
This diagram illustrates an example of using a connector that is wirelessly connected to the phone on one end, and to your hearing aid on the other end. ON this case, it is all done by RF (radio frequency) communication.
I write this for the sake of hearing aids users that find themselves confused by all the wireless terminology and misunderstandings. Therefore, I try to keep things as simple as possible and I simplify things to make them clearer. In addition, the discussion here is in the context of hearing aids and hearing aids’ users. I don’t try to cover the entire wireless world here, and therefore, all the data is observed from the angle of a hearing aid user and for his/her benefit.