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During the nineteenth century, the mechanization of farming and the fencing of range land opened the agriculture heart of North America to intensive development. A the natural geographic center of this region, Chicago became the crossroads of the vast transportation network. The great Lakes were linked in Chicago in 1847, When the Illinois Michigan canal was opened to traffic---
It is true that electronics developed from the study of electricity. Early ideas about the way electric current could flow through conductors and through a vacuum led to the development of useful radio systems and telephones. It was possible to send messages with what was, by today's standards, incredibly simple and crude equipment. The Second World War provided an urgent requirement for more 2 sophisticated communication and other electronic systems. The invention of radar required a big step forward in theory and even bigger step forward in engineering. The study of electronics gradually became an important study in its own right, and the radio engineer became a specialized technician The post-war development of television led to one of the most massive social changes that have ever taken place: many households became the owners of televisions, as well as radios and record players. In some branches of industry, electronic systems were regarded as useful, but electronic systems not directly concerned with wireless or television were still unusual. Only in the early 1960s did electronics technology really come of age', thanks to the work of three scientists working in the Bell Laboratories in the USA: Bardeen, Brattain, and Shockley. In 1957 they assembled the first working transistor
Although speech is the most advanced form of communication, there are many ways of communicating without using speech. Signals, signs, symbols, and gestures may be found in every known culture. The basic function of a signal is to impinge upon the environment in such a way that it attracts attention, as, for example, the dots and dashes of a telegraph circuit. Symbols are more difficult to disciple than either signals or signs because of their intricate relationship with the receiver's cultural perceptions. In some cultures, applauding in a theatre provides performers with an auditory symbol of approval. Gestures such as waiving and had shaking also communicate certain cultural messages.
