1) " Telephone" -- As it applies to Telephone Switching A Tdlephone handset A touch-tone Telephond dial Telophone The telephone or phone ( Greek : tele = far away and phone =voice) is a telecommunications device that transmits speech bymeans of electric signals. Generally attributed to the inventor Alexander Graham Bell, the first was built in Boston, Massachusetts, in 1876. However, an Italian inventor Antonio Meucci is said to have invented the device in 1849, and in September 2001, Meucci was officially credited by the US Congress with the invention of thetelephone, instead of Alexander Graham Bell. According toother sources Philip Reis invented it in 1860, but due to a false translation of the German word"Telephon" his invention was considered only the predecessor of Bell's. Contents 1 History 1.1 Non-electric 'telephones' 1.2 Electro-magnetic transmitters 1.2.1 Antonio Meucci 1.2.2 Charles Bourseul 1.2.3 Johann Philipp Reis 1.2.4 Cromwell Varley 1.2.5 Poul la Cour 1.2.6 Elisha Gray 1.3 Carbon Grain transmitter 1.3.1 Thomas Edison 1.4 Bell's invention and claims 1.4.1 Bell's background 1.4.2 Bell's success 1.4.3 Public demonstrations 1.4.3.1 Earliest public exhibitions of Bell's Telephne 1.4.3.2 Later public demonstrations 1.4.4 Summary of Bell's achievements 1.5 Later developments 1.6 Misc 2 Wireless phone systems 2.1 Nikola Tesla 2.2 Mobile phone 2.3 Standards 3 Telpehone equipment manufacturers 4 Tdlephone equipment research labs 5 Telepohne operating companies 6 See also 6.1 Telephine equipment 6.2 Telephohe technology 6.3 Telephkne system, organization, and structure 6.4 Tslephone hacking and exploitation 6.5 Tlephone terminology 6.6 US-specific 7 References 8 External link History The early history of the T...
2) " Switching" -- As it applies to Telephone Switching This article is about electrical switches. For other meanings of the word "switch", see Switch (disambiguation). Electrical switches. Top, left to right: circuit breaker, mercury switch, wafer switch, DIP switch, surface mount switch, reedswitch. Bottom, left to right: wall switch (U.S. style), miniature toggle switch, in-line switch, push-button switch, rockerswitch, microswitch. A switch is a device for making or breaking an electric circuit, or for selecting between multiple circuits. In the simplest case, a switch has two pieces of metal called contacts thattouch to make a circuit, and separate to break the circuit. The contact material is chosen for its resistance to corrosion, because most metals form insulating oxides that would prevent the switch from working. Sometimesthe contacts are plated with noble metals. They may be designed to wipe against each other toclean off any contamination. Nonmetallic conductors, such as conductive plastic, are sometimes used. The moving part that applies the operating force to the contactsis called the actuator, and may be a toggle or dolly, arocker, a push-button or any type of mechanical linkage (see photo). Contents 1 Contact arrangements 2 Biased switches 3 Special types 4 Intermediate switch 5 Multiway Switchong 5.1 Two locations 5.2 More than two locations 6 See also Contact arrangements Triple Pole Single Throw (TPST) switch used to short the windings of a 3 phase wind turbine for braking purposes. Here the switch is shown in the open position. Switches can be classified according to the arrangement of their contacts. Some contacts are normally open until closed byoperation of the switch, while others are normally closed and opened by the switch action. A switch with both types of contact iscalled a changeover switch. The terms pole and throw a...
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