2. Tin Foil Phonograph The first great invention developed by Thomas Edison in Menlo Park was the tin foil phonograph. While working to improve the efficiency of a telegraph transmitter, he noted that the tape of the machine gave off a noise resembling spoken words when played at a high speed. This caused him to wonder if he could record a telephone message. He began experimenting with the diaphragm of a telephone receiver by attaching a needle to it. He reasoned that the needle could prick paper tape to record a message. His experiments led him to try a stylus on a tinfoil cylinder, which, to his great surprise, played back the short message he recorded.

3. Tin Foil Phonograph

4. Electricity and Light Bulb Thomas Edison's greatest challenge was the development of a practical, electric light. He did not invent the light bulb, but rather he improved upon a 50-year-old idea. In 1879, using lower current electricity, a small carbonized filament, and an improved vacuum inside the globe, he was able to produce a reliable, long-lasting source of light. The idea of electric lighting was not new, and a number of people had worked on, and even developed forms of electric lighting. But up to that time, nothing had been created for a use at home. Thomas Edison's eventual achievement was inventing not just a electric light, but also an electric lighting system that contained all the elements necessary to make the light practical, safe, and affordable. After one and a half years of work, success was achieved when an lamp with a filament of carbonized sewing thread burned for thirteen and a half hours.

5. Light Bulb

6. The Electric Pen Thomas Edison created the electric pen in 1875. The motor drove a small needle up and down the handle of the pen, and as the user wrote, it created a stencil. This stencil was then placed in the press, and a roller was used to scrape ink through the holes in the stencil, creating a copy of the document.

7. Electric Pen

8. The Storage Battery During the first decade of the twentieth century, Edison spent much of his time developing a storage battery that he intended for use in electric automobiles. He was among the first to try to design consumer-friendly primary batteries in connection with his electric pen copying system and his electric phonograph, but he was never able to overcome the problems presented by the need to replenish chemicals and electrodes in wet cells. Edison also investigated storage batteries in the early 1880s in connection with central stations but decided that they were not efficient for that purpose. The advertisement of automobiles in the late 1890s spurred him to develop a storage battery to power them. It took him a decade to develop a viable iron- nickel battery and by that time automobiles powered by internal combustion engines had become dominant. The storage battery was the most success invention of his life.

9. Automobile Powered by Storage Battery

10. Diagram of Storage Battery

11. The End