loudspeaker

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Electromechanical device that converts electrical signals into sound waves, which are radiated into the air. The most common type of loudspeaker is the moving-coil speaker. Electrical signals from, for example, a radio are fed to a coil of fine wire wound around the top of a cone. The coil is positioned between the poles of a permanent magnet. When signals pass through it, the coil becomes an electromagnet, experiencing a force at right angles to the direction of the current and magnetic field, causing the coil to move. As the signal varies, the coil and the cone vibrate, setting up sound waves. If the electrical signals have a frequency of 2,000 hertz (Hz), sound with a frequency of 2,000 Hz is produced.

Black, red, and green are known as the ‘black liberation’ colours, recalling Jamaican black activist Marcus Garvey. Taken from the arms of Nyasaland, the sun indicates the dawning of a new era. Effective date: 6 July 1964. >>