| 摘要 |
The audio frequency music signal is fed via a low pass filter to an amplifier, to select only the bass rhythm. The amplifier output is fed via a rectifier and buffer to a thyristor circuit which controls an electric motor. The motor shaft is attached to one end of a flexible belt. The other end of the belt is wrapped around a spindle which is mounted in a frame. The spindle is attached at right angles to a lever which is held back against the frame by a spring. - When the music amplitude is hight, it causes the motor to wind the belt around its spindle, thus turning the spindle and swinging the lever. When the thyristor stops conducting, the spring pulls the lever back and the belt unwinds on the motor shaft The light source is mounted on the outer end of the lever, and its beam sweeps backwards and forwards in time to the music. (Previously notified in Week 8609)
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