Chapter 3 Signalling Introduction

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Chapter 3 Signalling Introduction

  1. 1. Chapter 3 - Signalling Digital Revolution and the Death of Distance….
  2. 2. When Mr Jackson was at school… <ul><li>He spoke to his friend(s) by meeting them. The telephone was for special occasions… </li></ul><ul><li>To write to somebody meant posting a letter or postcard. It took anything from 1 day to 2 weeks to arrive. </li></ul><ul><li>For entertainment he would watch one of 3 channels on TV. Although there were 4 BBC radio stations and a local one! </li></ul><ul><li>He had a camera that took 26mm film. </li></ul><ul><li>He saw his first computer in 1988. He could make it beep. </li></ul>
  3. 3. How the world has changed since then…
  4. 4. But why is it all now possible? <ul><li>The answer is DIGITAL technology!!! </li></ul><ul><li>But what is ’DIGITAL’ ? </li></ul>
  5. 6. So what’s so special? <ul><li>Easy regeneration from noise: digital signals resist the effects of noise </li></ul><ul><li>Ability to be processed and encoded </li></ul><ul><li>Represent different kinds of information in the same way. </li></ul>
  6. 7. The digital signal is easily regenerated back to the original.
  7. 8. Sending Bits… <ul><li>When a digital signal is sent, it is sent as a stream of 1s or 0s. </li></ul><ul><li>These 1s or 0s represent something that exists, e.g. a fax or email message. </li></ul><ul><li>A fax machine samples a page of text or pictures (it treats them the same) </li></ul><ul><li>It converts the page to black or white pixels – these are given the value of 1 or 0 </li></ul>But how long does it take to send a fax?

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