They pick up the ambient sound and amplify. You select the direction the sound comes from, and the volume. Attaches via Bluetooth to phone, music player, etc. The device "microphones" for picking up sounds are in a collar around the neck. Thus, not too good for a typical land-line phone. Though, one could hold the phone upside down, with the hearing speaker near the collar, and mouth piece in fromt of the mouth to work.