Electronic Data Communication

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Electronic Data Communication

• Between computers
• - e-mail
• - EPOS terminals
• - cash dispensers
• - facsimile
• - video conferencing
• Between CPU and peripherals e.g.
• - printer
• - robot
•  
• Transmission methods
• - Serial / parallel
• - Synchronous / asynchronous

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• Handshaking The exchange of signals between
  devices to establish their readiness to send or
  receive data
• Modem (MOdulator / DEModulator)A device which
  translates digital signals from the computer to
  analogue signals for transmission over an
  ordinary phone line, and back to digital at the
  receiving end.
• ISDNIntegrated Services Digital Network (high
  bandwidth)
• This is a network that is capable of sending
  voice, video and computer data. It has a high
  bandwidth to enable this.
• Data compression reduces the number of blocks
  transmitted. It works basically by replacing
  repeated bytes by one copy of the byte plus count
  of the number of repetitions.
• Protocol a strict set of rules for data
  transmission. It covers standards for physical
  connections, cabling, mode of transmission,
  speed, data format, error detection and
  correction.

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Factors Affecting Rate Of Data Transmission 

• The speed of the modem. Different modems provide
  different data transmission rates, varying
  typically between 9K bps (bits per second) to 56K
  bps
• The nature of the transmission line. A digital
  line such as an ISDN line has a much higher
  transmission speed than an analogue line
• The type of cable used. Twisted pair cable has a
  transfer rate of about 10Mbps, whereas fibre
  optic cable is about 10 times as fast
• The type of transmission, synchronous or
  asynchronous

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• To connect to a LAN, a computer must be equipped
  with special hardware and software. In the
  hardware department the computer needs a Network
  Interface Card (NIC)
• Network Interface Card (NIC) a computer circuit
  board that is installed in a computer so that it
  can be connected to a network. Most NICs are
  designed for a particular type of network,
  protocol, and media. Personal computers and
  workstations on a local area network (LAN)
  typically contain a network interface card
  specifically designed for the LAN transmission
  technology, such as Ethernet or token ring.

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Hubs

• This is a central wiring concentrator. A common
  connection point for devices in a network that
  takes an incoming signal and repeats it on all
  other ports. Hubs operate at the physical layer.

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Routers

• Used to connect the same or different networks.
  Used on the web to route traffic, or for the
  connection of a LAN to a WAN. Some routers can
  handle interconnecting LANS of different
  architectures, whether or not they use the same
  or a different protocol.

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Bridges

• Used to block or let through signals. Can be
  used as an expensive repeater. Depending on the
  type, some bridges are only able to handle the
  same protocol but others can handle different
  protocols. Eg. Ethernet Token Ring

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