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Audio data Text data Graphical data Video data In order for data transmission to occur, there must be a transmission line, also called transmission channel or channel, between the two machines. Data that is sent from one computer to another is simple, but if several machines are involved, this requires several transmission lines. This process is called multi-plexing Types of Data

Local Area vs. Wide Area Computers in our schools are connected in what would be called a local area. This works well because of the short distances. Wide areas would cover computers that were several miles apart. The major problem with this situation is that over distance data transmission speed decreases and shorter distances tend to have greater reliabilty. Fiber optic cables have helped increase not only speed but also reliabilty.

Introduction to digital transmission Digital transmission is the sending of information over a physical communications media in the form of digital signals. Analogue signals must therefore be digitised first before being transmitted. However, as digital information cannot be sent directly in the form of 0s and 1s, it must be encoded in the form of a signal with two states, for example:

Analog Transmission Data transmission takes two distinct forms, Analog vs Digital. Analog uses signals that carry sound waves or pictures. These forms of information are then carried via either wires or wireless tools to receiving units. The signal strenght varies based on frequency or amplitude. Digital Transmission The first form of digital transmission of information was the Morse code. Digital transmission of information utilizes binary code to transmit data (1/0)

Popular Choices Of Data Transmission Fire Wire FireWire, uses a "Peer-to-Peer" architecture in which the peripherals determine the most effective device for the transfer of information. This will enable a smooth and efficient dissemination of information. Hi-Speed USB 2.0 uses a "Master-Slave" architecture in which the computer itselft determines the best means of data transmission. The CPU selects from the peripherals that are attached to the machine. This tends to slow the transmission of data and further impacts the CPU

Fire Wire

This style of connection has been the industry standard for 13 years and serves as one of the most vital data transmission devices. USB offers internal power options wich allow devices to utilize the power of the CPU to run the device. USB 2.0 transmitts data at 480 Mbps. USB connections now face stiff competition from wireless connections, but as things stand, its effects are still being felt through out the world. Universal Serial Bus (USB)

Computer Switch Ethernet Hub

USB Connections

Upload and download Download refers to data transfer from the server to your computer and upload refers to data transfer from your computer to the server. It is of interest to know that upload and download occur on separate transmission channels (whether this be on a modem or on a special-purpose line). So, when you are sending (uploading) a document you are not losing any download bandwidth! The principles of analogue transmission Analogue data transmission consists of sending information over a physical transmission medium in the form of a wave. Data is transmitted via a carrier wave, a simple wave whose only purpose is to transport data by modification of one of its characteristics (amplitude, frequency or phase), and for this reason analogue transmission is generally called carrier wave modulation transmission. Three types of analogue transmission are defined depending on which parameter of the carrier wave is being varied:

Data Transmission Rates Per/Sec

Cabling types Several physical data-transmission media are available to connect together the various devices on a network. One possibility is to use cables. There are many types of cables, but the most common are: Coaxial cable Double twisted pair Optical fibre Coaxial cable Coaxial cable has long been the preferred form of cabling, for the simple reason that it is inexpensive and easily handled (weight, flexibility,...).

Optical fiber is a cable with numerous advantages: Light-weight Immune to noise Low attenuation Tolerates data rates on the order of 100 Mbps Bandwidth from tens of megahertz to several gigahertz (monomode fibre) Fibre optic cabling is particularly suited to links between distributors (central link between several buildings, known as backbone) as it allows connections over long distances (from several kilometres to 60 km in the case of single-mode fibre) without requiring earthing. Furthermore, this type of cable is very secure as it is extremely difficult to tap in to such a cable. However, despite its mechanical flexibility, this cable type is not suitable for local network connections as it is difficult to install and is very expensive. For this reason, twisted pair or coaxial cable are preferred for short links.