The microphone is your first point of contact with the sound, and it is a false economy to skimp on this vital part of the system. Instead, a parabolic microphone places a small audio receiver at the focus by attaching it to the end of a long plastic arm. The audio receiver connects via wire to an amplifier circuit which plugs into a set of ear phones worn by the user. To operate the parabolic microphone, the user simply spies his target from far off and aims the dish directly at it. However, due to the distance, even a slight turn of the device could throw it a few feet off course. For more information you can refer this link.