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Consumer Electronics by S. P. Bali

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CHAPTER 38

SWITCHING SYSTEMS

Telephony was invented in the 1870s; all the early exchanges used human operators to establish and supervise calls. As networks grew it became impractical to continue to use people to set up telephone calls. It has indeed been calculated that to carry today's telephone traffic using 19th century practices would need more than half the total population of all major cities to be employed as telephone operators.

Modern telephones are a far cry from Bell's original model and even from the ones available a couple of decades ago. They vary in shape and features. They have push buttons instead of dials and memories to store telephone numbers. Some are cordless—the handset is not attached to the base unit, but is linked ...

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