|PDH Online Course Description||PDH Units/
Learning Units (Hours)
When Thomas Alva Edisonís newest invention Ė the phonograph, was displayed in Machinery Hall at the 1889 Paris Exposition Universalle, it proved to be nearly as popular as the expositionís centerpiece; the Eiffel Tower. For the first time, recorded sound could be produced upon demand, enough to confuse Edisonís own dog who famously heard his masterís voice through the cone speaker of the phonograph. This image became the symbol of the Radio Corporation of America (RCA) Ė the pioneer in sound recording.
First wax cylinders were used then the 78rpm flat-disc record was introduced in the early 20th Century. Through a complex process of recording sound onto a wax disc and making master, mother and stamping discs (the latter for mass production), 78rpm records were manufactured in quantity from their main ingredient; powdered shellac (and nineteen other materials). They brought the music hall into homes but were monaural (sound from one source), scratched easily and were fragile to handle.
In the post-WWII years, shellac/78rpm records gave way to the long-play 33&1/3rd vinyl record which was more durable, longer playing and less likely to fracture like a glass dish if dropped. By the mid-1950s, stereophonic records were introduced whereby two sound sources could be cut into a single groove providing a high-fidelity stereo sound. Soon after, the cartridge tape made its appearance making recording/playback much easier and convenient, but with the same richness of sound as a hi-fi record (and they didnít scratch!).The Wizard of Menlo Park Ė and his dog, would approve.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
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