Data transmission equipment
1) - ) Modem is an acronym for DEModulate / MODulate
Know modems as of the leading means of linking computers and communication systems different, and the modem is a small device comes with two kinds:
the first type is a card integrates into the computer through port serial connection (serial port) in the motherboard, and quickly comes 56 kilometers bytes per second, which is a reasonable speed has the potential to meet the needs of the user to surf the Internet and other,
second type of modems is the external modem and the advantage of this modem multiple choices and price relatively high, where he works such as a fax machine, in which you can send a fax and receive any fax message without the condition that the computer is working, also there are types of modems operate tool integrated with the phone, where it can play the role of devices automatic reply (Answering Machine)
and there are other types of this kind can see and monitor the status and quality of contact with providing greater speed of communication, and the characteristics of this device that can work revealing the figures, any it could be on the way to know your numbers related. All modems are two ports (LAN) is a special phone line compass, which is used by the device when an external connection request or receive a call, the other port is (phone) and its work is to provide a home phone can be connected or connecting other devices.
The role of network card is the following matters:
1 - ) preparing data transmitted over the network.
( 2 - Send data on the network.
( 3 - control the flow of data between the computer and the dispatch center.
4 - ) translate electrical signals from the wire network bytes understood by thecomputer's processor, and when you want to send data, it translates digital computer signals into electrical pulses can wire network to carry.
Every network card has a unique network address, and this address determined by the IEEE committee and this committee allocates a range of addresses for each plant manufacturers of network cards. The publication entitled card on the network, allowing for Baltkhatab devices with each other and routing data to the intended destination.
Network card contains all of the physical parts Hardware and software parts Firmware Software, and this part be stored inside the compiler ROM memory and be responsible for directing and carrying out the tasks entrusted to the card.
The network card organizing the transmission of data on the network and by doing the following steps:
1 - ) the transfer of data from the computer to the card.
2 - ) temporarily store data on the card as a prelude to broadcast to the wire.
3 - ) an understanding on the conditions for the transfer of data between the card sending and receiving card.
4 - ) control the flow of data on the network.
Criteria that must be agreed upon by the cards in order to contact them are:
1 - ) the maximum size of data sets that will be sent.
2 - )The amount of data that will be sent prior to obtaining confirmation of arrival.
3 - ) the time interval between sending data packets.
4 - ) period of time to wait before getting to confirm the arrival of the data.
5 - ) the amount of data that can each card received before overflowing Overflow.
6 - ) speed data transfer.
After that is the agreement on these standards is the exchange of data between cards
3 - ) central Transport (Transmission Media)
Which is the medium used to connect computers to each other and which is the transfer of data.?
Among transportation types:
1 - ) wired circles
Scheduled wire (Twisted Pairs): a telephone wire and need a modem.
Coaxial wire (Coaxial): They are similar to your router to your TV cable and need a network card.
Optical fiber (Fiber Optics): a thin glass tube in which data is transferred at the speed of light and is used in wide area networks.
2 - ) Wireless circles:
Transport using radio waves.
Transport using the microwave.
Transport via satellite
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