Write a essay on the telaphone

telephone

Telephone, an instrument designed for the simultaneous transmission and reception of the human voice. The telephone is inexpensive, is simple to operate, and offers its users an immediate, personal type of communication that cannot be obtained through any other medium. As a result, it has become the most widely used telecommunications device in the world. Billions of telephones are in use around the world. The word telephone, from the Greek roots tēle, "far," and phonē, "sound," was applied as early as the late 17th century to the string telephone familiar to children, and it was later used to refer to the megaphone and the speaking tube, but in modern usage it refers solely to electrical devices derived from the inventions of Alexander Graham Bell and others. Within 20 years of the 1876 Bell patent, the telephone instrument, as modified by Thomas Watson, Emil Berliner, Thomas Edison, and others, acquired a functional design that has not changed fundamentally in more than a century. Since the invention of the transistor in 1947, metal wiring and other heavy hardware have been replaced by lightweight and compact microcircuit. Advances in electronics have improved the performance of the basic design, and they also have allowed the introduction of a number of "smart" features such as automatic redialing, call-number identification, wireless transmission, and visual data display. Such advances supplement, but do not replace, the basic telephone design. That design is described in this section, as is the remarkable history of the telephone's development, from the earliest experimental devices to the modern digital instrument. As it has since its early years, the telephone instrument is made up of the following functional components: a power source, a switch hook, a dealer, a ringer, a transmitter, a receiver, and an anti-side tone circuit. These components are described in turn below. In the first experimental telephones the electric current that powered the telephone circuit was generated at the transmitter, by means of an electromagnet activated by the speaker's voice. Such a system could not generate enough voltage to produce audible speech in distant receivers, so every transmitter since Bell's patented design has operated on a direct current supplied by an independent power source. The first sources were batteries located in the telephone instruments themselves, but since the 1890s current has been generated at the local switching office. The current is supplied through a two-wire circuit called the local loop. The standard voltage is 48 volts.