Edison and the Electric Chair_ A Story of Light and Death - Mark Essig [9]
R. F. Outcault's illustration of Edison's laboratory complex in Menlo Park, New jersey, as it appeared in 1881. The long building in the center is the main laboratory.
The first major invention to emerge from Menlo Park was a refined version of the device Alexander Graham Bell had first unveiled in 1876: the telephone. In Bell's telephone transmitter, the sound waves of the human voice vibrated a metal diaphragm, which induced an electric 21 current in an electromagnet. The current traveled over a wire and into a receiver, which essentially was a transmitter in reverse—an electromagnet vibrated a metal diaphragm, which (at least in theory) reproduced the original sound. Early users of Bell's telephone found, however, that voices emerging from the receiver were nearly unintelligible. The problem, Edison discovered, was the transmitter's electromagnet, which did a poor job of translating sound waves into electric current. Sensing an opportunity to win a patent on a crucial component of the telephone, Edison began experimenting on transmitters. He found that by replacing the electromagnet with buttons of compressed carbon, he could faithfully reproduce the modulations of the human voice. Edison's new carbon transmitter transformed the telephone from a novelty into a practical means of communication-and soon provided him with a fresh stream of income.
The telephone work led directly to another invention. At the time, when telephones were still largely in the experimental stage, no one had imagined a day when the instrument would be in every home and office, allowing people to speak directly to each other. Edison, like most other observers, expected that the telephone would function just as the telegraph system did, with an operator transcribing a voice message and delivering it to the recipient. The electrical pulses of a telegraph message could be preserved and replayed at a later time; Edison believed a telephone system should have a similar capability. The goal, as Edison described it in July 1877, was to "store up St reproduce automatically at any future time the human voice."13
Edison earlier had invented a device to record the electrical impulses of telegraph messages on waxed paper tape, and he also knew that the human voice created vibrations in the diaphragm of a telephone transmitter. He decided to see if these vibrations, like the telegraph messages, could be embossed and repeated. Late in 1877 Edison designed a lathelike machine consisting of a cylinder wrapped with tinfoil and attached to a hand crank. There were two diaphragms, each attached to a needle. One needle would emboss the sound waves into the foil; the other, in passing over the indentations, would reproduce the original sound.
One of the Menlo Park workers built the device to Edison's specifications, and it surprised everyone by working the first time it was tried. Edison called it the phonograph, or "sound writer."
Edward H. Johnson, a business associate of Edison's since the early 1870s and a master showman, took charge of promoting the phonograph in public exhibits up and down the East Coast. The concept was so novel that many people refused to believe it. A Yale professor insisted that the "idea of a talking machine is ridiculous" and advised Edison to disavow published accounts of the phonograph in order to protect his "good reputation as an inventor." Many were convinced that Edison was simply a ventriloquist, throwing his voice into the machine. A visiting minister rapidly shouted a tongue-twisting string of biblical names into the phonograph; only when the machine spit them back precisely did he believe that Edison had no tricks up his sleeve. On an April