Marlon

= =  v Computers and devices on a network require some form of communications link to allow electronic signals to pass between them.

Early networks were always connected by wires and cables. Cables are used within buildings and underground to connect remote buildings.

 v Most star networks use an unshielded twisted pair (UTP) cable.  v There are 8 wires twisted into 4 separate pairs and then twisted as a group.  v The twisting helps to prevent outside interference.  v CAT 3- 10mbps over 100m. CAT 5- 100mbps over 85m. CAT 5e uses all four wire pairs and supports up to 1GB. 

 v Contains only two wires- the inner wire is surrounded by insulation, copper braid and more insulation. It is commonly used to connect a TV to the aerial.  v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Coaxial cable can carry 10mpbs over 185m. <span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l2 level1 lfo8; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Used in Bus networks, where data travels in both directions so the cable carries both incoming and outgoing messages from each computer on the same wires. <span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l2 level1 lfo8; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Thus it takes longer for a device to send a message over the network.

<span style="line-height: normal; margin: 0cm 0cm 0pt 36pt; mso-list: l3 level1 lfo9; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Consists of special glass or plastic strands that can transmit light pulses and can transmit data for up to 2km. <span style="line-height: normal; margin: 0cm 0cm 0pt 36pt; mso-list: l3 level1 lfo9; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">The speed of data relies on the quality of the light generator and light receiver on the ends of the strand. <span style="line-height: normal; margin: 0cm 0cm 0pt 36pt; mso-list: l3 level1 lfo9; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Fibre optic strands are only capable of handling one-way traffic thus when two way traffic is required two separate strands are used.

<span style="line-height: normal; margin: 0cm 0cm 0pt 36pt; mso-list: l5 level1 lfo1; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Wireless transmission is used where it is difficult to install cables.

<span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l7 level1 lfo2; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Can be transmitted long distances like between buildings or between cities. <span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l7 level1 lfo2; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">A transmitter is needed to broadcast the radio signal and a receiver is needed to accept it. <span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l7 level1 lfo2; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Wireless communications are slower than cable connections. <span style="line-height: normal; margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l7 level1 lfo2; text-align: justify; text-indent: -18pt;"> v ** <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Bluetooth **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> uses short range radio waves to transmit data over a distance of up to 10m

v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Require line of sight transmission where there is no obstruction between the sending dish and the receiving dish. v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">A microwave station contains a “dish” with an antenna, receivers and other equipment and are located on towers, hills or on top of buildings.

v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Satellite transmission can be in the form of radio waves or microwaves. v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">A limitation of this form of transmission is the distance the waves have to travel to the satellite and back to the earth station. v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">A station (on earth) transmits the signal to the satellite (in space) which then strengthens (amplify) the signal and sends it back.

<span style="margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l1 level1 lfo5; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Is effective over short distance of up to 5m and has a slow data transfer rate. <span style="margin: 0cm 0cm 0pt 54pt; mso-add-space: auto; mso-list: l1 level1 lfo5; text-align: justify; text-indent: -18pt;"> v <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Uses light waves and requires line of sight access.