Le Developpement

I-) Introduction

The phone is a communication device , originally designed to transmit the human voice and allow conversation distance .

To function, the phone requires a terrestrial or space infrastructure , the telephone network. After having connected the fixed terminal or switched their mobile device , the user having entered into a contract with a telecommunications operator can make a phone call to a recipient also connected by dialing appointed , which usually triggers Send the destination device . If the called party accepts the call, a telephone conversation can begin , which is usually in French , the word "Hello ."

Except for emergency calls made to special numbers, calls made via telephone at a cost, which is determined by call established according to their duration , location of the recipient of the quality issue rates. Telephony and is an important market in the telecommunications sector .

II-) The phone manual

The ancestor phones

At its inception, the telephone network was completely manual . Calling a correspondent was performed by the following procedure:

the subscriber lifts the handset of the phone ,

This action causes the downfall of a central annunciator panel , sometimes the lighting of a lamp ,

an operator responds to the subscriber note the number of the call :

if the corresponding dependent even central , connecting with the subscriber will "local"

otherwise, the operator calls another attendant in charge of the central office of the person called .

The call button has been gradually replaced by a magneto . Its role is to produce an electrical voltage to bring down the central part of the annunciator . The advantage over the call button is the removal of cells present in the subscriber service which was particularly expensive.

III-)Automatic telephone

Automatic telephone was invented by Almon Strowger , the United States around 1891 . Thereof, mortician , suspecting Operators favor its competitor, wanted to eliminate manual operations when establishing a call. Auto switch will be tested in France in 1912 in Nice.

The advantage of automatic phone call someone directly without going through an operator . The user picks up the handset of the phone and then transmitted to a machine with a movable dial, the series of numbers identifying its corresponding ( telephone number ) .

When switching to automatic in Paris, a three-digit number was assigned to each telephone exchange. Subscribers should dial three digits, then the number of their correspondent. As followers had in mind the names of their corresponding central , we wrote on the dials dialing devices , some letters of the alphabet for each chiffre5 , which allowed to keep a long tradition , giving its number

of give the name of the central example Danton and not the corresponding number 326. It was nevertheless call the operator by 16 relations " trunk " and 19 for relations "international"

Mobile phone [ edit the code]

IV-)Mobile phones.

Mobile originated in the 1950s in the United States. The first networks require the allocation of a frequency communication, and geographic areas were large (few subscribers per unit area). Thereafter, cellular networks have enabled a more rational use of frequencies, thus increasing significantly the capacity of networks.

In addition to the conventional telephone communication, the mobile phone has developed other features such as sending short texts (SMS) and web access.

VI-)Why the dependence

If teenagers are the most affected

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