• In a network, a communication channel is a physical path the transmission signals travel.
    • It is the path information travels from computer to computer.
    • How do the computers in a network “connect” to each other.

The 5 communication channels

  • twisted-pair cables
  • coaxial cables
  • fiber optic cables
  • terrestrial stations
  • communication satellites

Twisted pair cables

  • Signals are transmitted using pairs of independently insulated wires that have been physically twisted together
  • Used by older telephone networks
  • Network cables use an RJ-45 jack for four pairs of twisted-pair cables.

Coaxial cables

  • Core of the wire is copper
  • High frequency signals can be carried on a single cable – used for video transmission
  • Used when twisted pair cabling is not adequate to carry the required amount of data.

Fibre Optic Cables

  • Digital signals are sent as light pulses which are translated back into electrical signals
  • Composed of fine glass strands
  • The Centre core is composed of: Fine glass strand surrounded by glass cladding and protective layer
    • Glass cladding reflects light back into the core, guiding the light along the wire
  • Thousands of transmissions can be carried on a single strand
  • Can transmit signals faster than twisted pair and coaxial cables

Terrestrial Stations

  • Information is sent via microwaves from ground based transmitting and receiving stations
    • Text, sound, and graphics are converted into microwave pulses and transmitted
  • Microwave stations (a.k.a. repeater stations)  must be placed every 50 kilometres to receive, amplify, and then pass the signal along
  • Transfer information at much higher speeds than cabling

Communication Satellites

  • Orbiting around earth
  • Avoids cost of cabling and repeater stations
  • Minimum of three satellites are needed to provide world-wide communication
  • Transfer information at much higher speeds than cabling

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