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Wednesday, July 7, 2010
Sunday, June 20, 2010
Service
In the United States and Canada, universal service was a stated goal of the telephone industry during the first half of the 20th century—eve
ry household was to have its own telephone. This goal has now been essentially reached, but before it became a reality, the only access many people had to the telephone was through telephones, usually placed in a neighborhood store. A pay telephone is a telephone that may have special hardware to count and safeguard coins or, more recently, to read the information off credit cards or calling cards. Additional equipment at the exchange responds to signals from the pay phone to indicate to the operator or automatic exchange how much money has been deposited or to which account the call will be charged. Today the pay phone still exists, but it usually serves as a convenience rather than as primary access to the telephone network. The explosive growth of cell phones has greatly reduced the use of pay phones. The FCC estimates that more than 1 million pay phones have been removed from service since the mid-1990s.
Computer-controlled exchange switches make it possible to offer a variety of extra services to both the residential and the business customer. Some servi
ces to which users may subscribe at extra cost are call waiting, in which a second incoming call, instead of receiving a busy signal, hears normal ringing while the subscriber hears a beep superimposed on the conversation in progress; and three-way calling, in which a second outgoing call may be placed while one is already in progress so that three subscribers can then talk to each other. Some services available to users within exchanges with the most-modern transmission systems are: caller ID, in which the calling party’s number is displayed to the receiver (with the calling party’s permission—subscribers can elect to make their telephone number hidden from caller-ID services) on special equipment before the call is answered; and repeat dialing, in which a called number, if busy, will be automatically redialed for
a certain amount of time.
For residential service, voice mail can either be purchased from the telephone company or can be obtained by purchasing an answering machine. An answering machine usually contains a regular telephone set along with the ability to detect incoming calls and to record and play back messages, with either an audiotape or a digital system. After a preset number of rings, the answering machine plays a prerecorded message inviting the caller to leave a message to be recorded.
ry household was to have its own telephone. This goal has now been essentially reached, but before it became a reality, the only access many people had to the telephone was through telephones, usually placed in a neighborhood store. A pay telephone is a telephone that may have special hardware to count and safeguard coins or, more recently, to read the information off credit cards or calling cards. Additional equipment at the exchange responds to signals from the pay phone to indicate to the operator or automatic exchange how much money has been deposited or to which account the call will be charged. Today the pay phone still exists, but it usually serves as a convenience rather than as primary access to the telephone network. The explosive growth of cell phones has greatly reduced the use of pay phones. The FCC estimates that more than 1 million pay phones have been removed from service since the mid-1990s.Computer-controlled exchange switches make it possible to offer a variety of extra services to both the residential and the business customer. Some servi
ces to which users may subscribe at extra cost are call waiting, in which a second incoming call, instead of receiving a busy signal, hears normal ringing while the subscriber hears a beep superimposed on the conversation in progress; and three-way calling, in which a second outgoing call may be placed while one is already in progress so that three subscribers can then talk to each other. Some services available to users within exchanges with the most-modern transmission systems are: caller ID, in which the calling party’s number is displayed to the receiver (with the calling party’s permission—subscribers can elect to make their telephone number hidden from caller-ID services) on special equipment before the call is answered; and repeat dialing, in which a called number, if busy, will be automatically redialed for
a certain amount of time.For residential service, voice mail can either be purchased from the telephone company or can be obtained by purchasing an answering machine. An answering machine usually contains a regular telephone set along with the ability to detect incoming calls and to record and play back messages, with either an audiotape or a digital system. After a preset number of rings, the answering machine plays a prerecorded message inviting the caller to leave a message to be recorded.
Making a call
A telephone call starts when the caller lifts a handset off the base. This closes 
an electrical switch that initiates the flow of a steady electric current over the line between the user’s location and the exchange. The exchange detects the current and returns a dial tone, a precise combination of two notes that lets a caller know the line is ready.
Once the dial tone is hear
d, the caller uses a rotary or push-button dial mounted either on the handset or base to enter a sequence of digits, the telephone number of the called party. The switching equipment in the exchange removes the dial tone from the line after the first digit is received and, after receiving the last digit, determines whether the called party is in the same exchange or a different exchange. If the called party is in the same exchange, bursts of ringing current are applied to the called party’s line. Each telephone contains a ringer that responds to a specific electric frequency. When the called party answers the telephone by picking up the handset, steady current starts to flow in the called party’s line and is detected by the exchange. The exchange then stops applying ringing and sets up a connection between the caller and the called party.
If the called party is in a different exchange from the caller, the caller’s exchange sets up a connection over the telephone network to the called party’s exchange. The called exchange then handles the process of ringing, detecting an answer, and notifying the calling exchange and
billing machinery when the call is completed (in telephone terminology, a call is completed when the called party answers, not when the conversation is over).
When the conversation is over, one or both parties hang up by replacing their handset on the base, stopping the flow of current. The exchange then initiates the process of taking down the connection, including notifying billing equipment of the duration of the call if appropriate. Billing equipment may or may not be involved because calls within the local calling area, which includes several nearby exchanges, may be either flat rate or message rate. In flat-rate service, the subscriber is allowed an unlimited number of calls for a fixed fee each month. For message-rate subscribers, each call involves a charge that depends on the distance between the calling and called parties and the duration of the call. A long-distance call is a call out of the local calling area and is always billed as a message-rate call.
an electrical switch that initiates the flow of a steady electric current over the line between the user’s location and the exchange. The exchange detects the current and returns a dial tone, a precise combination of two notes that lets a caller know the line is ready.Once the dial tone is hear
d, the caller uses a rotary or push-button dial mounted either on the handset or base to enter a sequence of digits, the telephone number of the called party. The switching equipment in the exchange removes the dial tone from the line after the first digit is received and, after receiving the last digit, determines whether the called party is in the same exchange or a different exchange. If the called party is in the same exchange, bursts of ringing current are applied to the called party’s line. Each telephone contains a ringer that responds to a specific electric frequency. When the called party answers the telephone by picking up the handset, steady current starts to flow in the called party’s line and is detected by the exchange. The exchange then stops applying ringing and sets up a connection between the caller and the called party.If the called party is in a different exchange from the caller, the caller’s exchange sets up a connection over the telephone network to the called party’s exchange. The called exchange then handles the process of ringing, detecting an answer, and notifying the calling exchange and
billing machinery when the call is completed (in telephone terminology, a call is completed when the called party answers, not when the conversation is over).When the conversation is over, one or both parties hang up by replacing their handset on the base, stopping the flow of current. The exchange then initiates the process of taking down the connection, including notifying billing equipment of the duration of the call if appropriate. Billing equipment may or may not be involved because calls within the local calling area, which includes several nearby exchanges, may be either flat rate or message rate. In flat-rate service, the subscriber is allowed an unlimited number of calls for a fixed fee each month. For message-rate subscribers, each call involves a charge that depends on the distance between the calling and called parties and the duration of the call. A long-distance call is a call out of the local calling area and is always billed as a message-rate call.
Today's Industry
In 1996 the U.S. government enacted the Telecommunications Reform Act, w
hich removed government rules preventing local and long-distance phone companies, cable television operators, broadcasters, and wireless services from directly competing with one another. The act spurred consolidation in the industry, as regional companies joined forces to create telecommunications giants that provided telephone, wireless, cable, and Internet services.
In other countries, until the 1990s, most of the telephone companies were owned by each nation’s central government and operated as part of the post office, an arrangement that inevitably led to tight control. Many countries are now privatizing telephone service. In order to escape government regulation at home, U.S. companies are investing heavily in the phone systems of other countries. For example, in 1995 AT&T announced it would attempt to gain a share of the market for telephone services in India. In a reverse trend, European companies are investing in U.S. long-dist
ance carriers.
Other major markets for telephone companies are opening up around the globe as the developing world becomes more technologically advanced. Nonindustrial countries are now trying to leapfrog their development by encouraging private companies to install only the latest technology. In remote places in India and Africa, the use of solar cells is now making it possible to introduce telephones in areas still without electricity
hich removed government rules preventing local and long-distance phone companies, cable television operators, broadcasters, and wireless services from directly competing with one another. The act spurred consolidation in the industry, as regional companies joined forces to create telecommunications giants that provided telephone, wireless, cable, and Internet services.In other countries, until the 1990s, most of the telephone companies were owned by each nation’s central government and operated as part of the post office, an arrangement that inevitably led to tight control. Many countries are now privatizing telephone service. In order to escape government regulation at home, U.S. companies are investing heavily in the phone systems of other countries. For example, in 1995 AT&T announced it would attempt to gain a share of the market for telephone services in India. In a reverse trend, European companies are investing in U.S. long-dist
ance carriers.Other major markets for telephone companies are opening up around the globe as the developing world becomes more technologically advanced. Nonindustrial countries are now trying to leapfrog their development by encouraging private companies to install only the latest technology. In remote places in India and Africa, the use of solar cells is now making it possible to introduce telephones in areas still without electricity
Parts
A basic telephone set contains a transmitter that transfers the caller’s voice; a recei
ver that amplifies sound from an incoming call; a rotary or push-button dial; a ringer or alerter; and a small assembly of electrical parts, called the antisidetone network, that keeps the caller’s voice from sounding too loud through the receiver. If it is a two-piece telephone set, the transmitter and receiver are mounted in the handset, the ringer is typically in the base, and the dial may be in either the base or handset. The handset cord connects the base to the handset, and the line cord connects the telephone
to the telephone line.
More sophisticated telephones may vary from this pattern. A speakerphone has a microphone and speaker in the base in addition to the transmitter and receiver in the handset. Speakerphones allow callers’ hands to be free, and allow more than two people to listen and speak during a call. In a cordless p
hone, the handset cord is replaced by a radio link between the handset and base, but a line cord is still used. This allows a caller to move about in a limited area while on the telephone. A cellular phone has extremely miniaturized components that make it possible to combine the base and handset into one handheld unit. No line or handset cords are needed with a cellular phone. A cellular phone permits more mobility than a cordless phone.
ver that amplifies sound from an incoming call; a rotary or push-button dial; a ringer or alerter; and a small assembly of electrical parts, called the antisidetone network, that keeps the caller’s voice from sounding too loud through the receiver. If it is a two-piece telephone set, the transmitter and receiver are mounted in the handset, the ringer is typically in the base, and the dial may be in either the base or handset. The handset cord connects the base to the handset, and the line cord connects the telephone
to the telephone line.More sophisticated telephones may vary from this pattern. A speakerphone has a microphone and speaker in the base in addition to the transmitter and receiver in the handset. Speakerphones allow callers’ hands to be free, and allow more than two people to listen and speak during a call. In a cordless p
hone, the handset cord is replaced by a radio link between the handset and base, but a line cord is still used. This allows a caller to move about in a limited area while on the telephone. A cellular phone has extremely miniaturized components that make it possible to combine the base and handset into one handheld unit. No line or handset cords are needed with a cellular phone. A cellular phone permits more mobility than a cordless phone.History
The history of the invention of the telephone is a stormy one. A number of inventors contributed to carrying a voice signal over wires. In 1854 the French inventor Ch
arles Bourseul suggested that vibrations caused by speaking into a flexible disc or diaphragm might be used to connect and disconnect an electric circuit, thereby producing similar vibrations in a diaphragm at another location, where the original sound would be reproduced. A few years later, the German physicist Johann Philip Reis invented an instrument that transmitted musical tones, but it could not reproduce speech. An acoustic communication device that could transmit speech was developed around 1860 by an Italian American inventor, Antonio Meucci. The first to achieve commercial success and inaugurate widespread use of the telephone, however, was a Scottish-born American inventor, Alexander Graham Bell, a speech teacher in Boston, Massachusetts.
Bell had built an experimental telegraph, which began to function strangely one day because a part had come loose. The accident gave Bell insight into how voices could be reproduced at a distance, and he constructed a transmitter and a receiver, for which he received a patent on March 7, 1876. On March 10, 1876, as he and his assistant, Thomas A. Watson, were preparing to test the mechanism, Bell spilled some acid on himself. In another room, Watson, next to the receiver, heard clearly the first telephone message: “Mr. Watson, come here; I want you.”
A few hours after Bell had patented his invention, another American inventor, Elisha Gray, filed a document called a caveat with the U.S. Patent Office, announcing that he was well on his way to inventing a telephone. Other inventors, including Meucci and Amos E. Dolbear, also m
ade claim to having invented the telephone. Lawsuits were filed by various individuals, and Bell’s claim to being the inventor of the first telephone had to be defended in court some 600 times. Gray’s case was decided in Bell’s favor. Meucci’s case was never resolved because Meucci died before it reached the Supreme Court of the United States.
arles Bourseul suggested that vibrations caused by speaking into a flexible disc or diaphragm might be used to connect and disconnect an electric circuit, thereby producing similar vibrations in a diaphragm at another location, where the original sound would be reproduced. A few years later, the German physicist Johann Philip Reis invented an instrument that transmitted musical tones, but it could not reproduce speech. An acoustic communication device that could transmit speech was developed around 1860 by an Italian American inventor, Antonio Meucci. The first to achieve commercial success and inaugurate widespread use of the telephone, however, was a Scottish-born American inventor, Alexander Graham Bell, a speech teacher in Boston, Massachusetts.
Bell had built an experimental telegraph, which began to function strangely one day because a part had come loose. The accident gave Bell insight into how voices could be reproduced at a distance, and he constructed a transmitter and a receiver, for which he received a patent on March 7, 1876. On March 10, 1876, as he and his assistant, Thomas A. Watson, were preparing to test the mechanism, Bell spilled some acid on himself. In another room, Watson, next to the receiver, heard clearly the first telephone message: “Mr. Watson, come here; I want you.”A few hours after Bell had patented his invention, another American inventor, Elisha Gray, filed a document called a caveat with the U.S. Patent Office, announcing that he was well on his way to inventing a telephone. Other inventors, including Meucci and Amos E. Dolbear, also m
ade claim to having invented the telephone. Lawsuits were filed by various individuals, and Bell’s claim to being the inventor of the first telephone had to be defended in court some 600 times. Gray’s case was decided in Bell’s favor. Meucci’s case was never resolved because Meucci died before it reached the Supreme Court of the United States.Friday, June 18, 2010
Types
There are various types of mobile phones based on their feasibility and working cri
teria. Some of them are: Basic Phones:Basic phones are the normal phones that we use containing facility of calling, messaging, alarm clock, calendar and some other normal requirements. These mobiles tend to offer a basic operating system that allows for calling, some music capabilities and carrier-specific applications. smartphone: smartphone are non-touch screen devices that offer a robust mobile operating system, most commonly Windows Mobile, Symbian, Blackberry or Palm. smartphone are capable of sending and receiving emails, editing documents and storing files. Pocket PC Devices: Pocket PC devices operate much like smartphone, though with touch screen abilities. 
GSM Technology:If your phone uses a SIM card, you are using GSM technology. This technology allows "unlocked" devices to swap SIM cards between carriers without having to notify the carrier of the new device. CDMA Technology:CDMA cell phones use an ESN (Electronic Serial Number) rather than a SIM card to identify the phone.In order to use the phone, you must call your carrier and they put the ESN on your account; they are notSwappable as easily as GSM devices.
teria. Some of them are: Basic Phones:Basic phones are the normal phones that we use containing facility of calling, messaging, alarm clock, calendar and some other normal requirements. These mobiles tend to offer a basic operating system that allows for calling, some music capabilities and carrier-specific applications. smartphone: smartphone are non-touch screen devices that offer a robust mobile operating system, most commonly Windows Mobile, Symbian, Blackberry or Palm. smartphone are capable of sending and receiving emails, editing documents and storing files. Pocket PC Devices: Pocket PC devices operate much like smartphone, though with touch screen abilities. 
GSM Technology:If your phone uses a SIM card, you are using GSM technology. This technology allows "unlocked" devices to swap SIM cards between carriers without having to notify the carrier of the new device. CDMA Technology:CDMA cell phones use an ESN (Electronic Serial Number) rather than a SIM card to identify the phone.In order to use the phone, you must call your carrier and they put the ESN on your account; they are notSwappable as easily as GSM devices.
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