Transmission Media

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Networking involves connection of computer, workstations and peripheral devices. networking hardware involves all the peripheral devices,

interface card and other equipment such as cables and wires that are used to establish a network connection. Wire is a single, cylindrical

strand of metal conductor with low resistance to the current flow. cable can be defined as a bunch of wires bound together which may be bare

or insulated. You can connect these devices either using physical transmission medium or using wireless transmission medium. Physical transmission media involves the use of wires and cables.



CHARACTERISTICS OF CABLES

  • Segment length :- Every cable has a limitation to carry signals only to a particular distance after which the quality the quality of the signal degrades and becomes corrupt. The capacity of the cable to carry signals to a certain distance till they can be regenerated using amplifiers or repeaters id known as the maximum segment length of that cable.
  • Attenuation :- As the signals travelthrough cables, they lose their strength. This loss of signal strength in a cable is called as attenuation. With more attenuation, the signal strength arriving at destination decreases. As the operating frequency and cable length increases, attenuation also increases. Attenuation is measured in DB and expressed as a negative value as it indicates a loss, for example – 12 DB
  • Bandwidth :- It is the amount of digital data that a cable can carry. Each type of cable can carry only a certain amount of information or data over a given period of time. This capacity is measured in terms of bandwidth. It is measured in terms of bits or bytes the cable can carry at a certain time. It is an important factor while selecting a network cable.
  • Cost :- cable come in different quality. Depending on the length, size of the network, you may need to choose the right type of cable. Copper cable are the cheapest form of cable, whereas fiber optic cables are the most expensive. Installation costs of copper cables are cheaper as compared to that of fiber optic cables.
  • Interference Susceptibility :- Each type of cable is susceptible to some interference such as internal or external noise. It depends on the environment where the cable is to be laid. External noise may consist of electromagnetic interference (EMI) or radio frequency interference (RFI) EMI refers to unwanted radiations or noise from external devices such as electric motors and relays. RFI refers to the radiation in the radio frequency range interfering with transmission over copper cables. In case of shielded cable, if the shield id not grounded properly, then it acts as an antenna and picks up such interference than the unshielded cables. Coaxial cables and shielded twisted pair cables are less susceptible to interference. Fiber optic cables are the least susceptible to interference.
  • Crosstalk :- It is interference caused when magnetic fields generated by the current flowing through one cable affects electrical currents of other cable. Cable crosstalk can result in signal distortion which leads towards network problems. Crosstalk can be reduced by twisting and shielding the wire pairs. In twisted pair cable the magnetic fields cancel each other to decrease the crosstalk.