Edison’s phonograph underwent constant innovation to become a popular electric phonograph. It is made up of the motor, the turntable, the receiver, and the vocalizer. When using, place the record on the turntable, let the motor run along with the turntable and the record rotates at a steady speed, and then place the recording unit on the disc. There are tracks on the disc that run in circles. On the recording unit, there is a singing needle. The needle runs in the track, following the groove variation, which produces the oscillation. This type of oscillation through the receiver converts to an electrical signal. The sound recorded on the disc is immediately generated from the speakers through the amplification of the pronunciation unit.
Using the laser to make the disc play the sound, its principle is very similar to the conventional gramophone. But their records and recorders are very different. The track of a popular record is very coarse, and the amount of information that can be recorded is minimal. When crafting a CD, focus the laser beam at a point less than 1 micron, and at the same time convert the audio signal into a digital code, controlling the laser beam to engrave each ring in circles on the representative metal thin disc. For marking 0 or 1.
This type of groove is only 0.4 microns wide, about 1 micron deep, the distance between the grooves is only 1.7 microns, roughly 1/40 of a hair. The record is made in this way, invisible on the face with the grooves and marks. Seeing through the thin plastic protective film covering the surface of the record, you can see an unusually bright multicolored light. To observe the groove and its etching, must use a microscope.
On the CD’s surface, there are hundreds of thousands of engravings on the area of the size of the sharp tip of the singing needle. Naturally, using a singing needle is impossible to recognize, so we must use a laser. Laser concentrates on the surface of the disc metal film, the ability to reflect the light of the metal film where there is etched and without etching is very different. Thus, when the disc begins to rotate, the reflected light occurs changes in each etch, through the photoelectric bulb turns into digital electrical signals formed by 0 and 1, and then through the wave point, amplifying. Great, reverting to the original audio signal. So it is possible to emit music from within the sound system.
Compared with traditional plastic discs, CDs have many unique advantages. Because its grooves are so small, they can hold a much larger amount of information than plastic discs. A CD 12 cm in diameter can play stereo music for an hour. It applies digitalization, fabricates high-fidelity digital stereo disc, the sound distortion is extremely small. Also, the disc surface is not scratched like traditional plastic discs.