# Chapter 1.  Understand bits, bytes, megabytes, etc.  Learn basic communication model.  Learn the distinction between channel, circuit and network.

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Chapter 1

 Understand bits, bytes, megabytes, etc.  Learn basic communication model.  Learn the distinction between channel, circuit and network.  Types of circuits.  Transmission modes (direction).  Transmission signals. Prepared by Saher H. Mohammed2

 Electronic communications happen in the form of bits (0’s and 1’s).  Collection of 8 bits is called byte.  Collection of 1024 bytes is called kilobytes.  Collection of 1024 kilobytes is called Megabyte.  Collection of 1024 megabytes is called Gigabyte. 3Prepared by Saher H. Mohammed

 To transmit data over a distance we need a sender ( source ), a communication medium ( channel ) and the receiver ( destination ). 4Prepared by Saher H. Mohammed

 Data communication is concerned with the actual (complete and accurate) transfer of data rather than the intent.  Data communication is machine-to-machine communication.  Telecommunication is the transfer of data over a distance via electrical, electromagnetic or photonic means.  Electromagnetic is radio waves.  Photonic means use of light instead of electricity or radio waves. Prepared by Saher H. Mohammed6

 A channel is a path, not necessarily a pair of wires, for transmitting between two or more nodes or points.  A channel connects the source to the destination.  A channel is a one way communication, and the transmission between the source and the destination can be electrical or photonic. 7Prepared by Saher H. Mohammed

 A circuit is a physical connection/ path between two nodes for communication.  A circuit may be a one-way communication or a two-way communication path and can be divided into multiple channels.  A circuit can be either wired or wireless.  A network consists of multiple paths to establish connections between multiple nodes. Prepared by Saher H. Mohammed8

9 Node TV StationTV Receiver Channel Terminal Computer Circuit

Prepared by Saher H. Mohammed10 Node Path  Each path may be a channel of a circuit

 Data terminating equipment (DTE) are non communications- oriented components of a data communication environment.  Data communication equipment (DCE) communications- oriented components of a data communication environment. Prepared by Saher H. Mohammed11

Prepared by Saher H. Mohammed12 DCE - Modem DTE – Computer/ Terminal Communication Signals

 Simplex: One way communication all the time.  Examples: are AM/ FM Radio and TV.  Half Duplex: One way communication at a time, but with a bidirectional capabilities.  Example: police car communicating with a base station.  Full Duplex: A simultaneous, bidirectional communication.  Example: telephonic conversations. 13Prepared by Saher H. Mohammed

 Parallel Circuits: The number of wires from a sender to a receiver is equal to or greater than the number of bits for a character.  Parallel Circuits provide faster communication.  Parallel Circuits are used in PC data bus. 14Prepared by Saher H. Mohammed

 Serial Circuit: All the bits are transferred from the sender to a receiver through a single wire.  Serial Circuits are cheap and cost effective. 15Prepared by Saher H. Mohammed

 Analog Signals are continuous in wave form.  Analog signals vary by time, called frequency.  Analog signals are measured in terms of cycles per second, called hertz(Hz).  Amplitude is distance between the crest and the through. 16Prepared by Saher H. Mohammed

 Digital signals use discrete levels of voltages.  They are also called a binary signals.  They are measured in teams of bits per seconds (bps). 17Prepared by Saher H. Mohammed

18Prepared by Saher H. Mohammed

 Bandwidth: the information carrying capacity of the circuit.  Noise: it is any unwanted signal.  Attenuation: it means the signal looses strength and becomes weaker as it travels down the channel.  Amplification: is the process of making the signal stronger. 19Prepared by Saher H. Mohammed

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