Assistive listening device
An Assistive listening device (ALD) is used to provide hearing ability for people in a variety of situations. A common usage is to aid people who are hard of hearing. The ALD may be used to help people hear televisions and other audio devices and also to help people hear speech through public address (PA) systems such as in church or at a lecture.
The assistive listening device is usually used as a system where the audio source is broadcast wirelessly over an FM frequency. The person who is listening may use a small FM Receiver to tune into the signal and listen at their preferred volume.
See also 
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