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2.1 What is a virus?

A virus is a piece of computer code – a program – that has been written to gain access to files or programs on your computer. The virus may enter your computer via floppy disk, by email or by your Internet connection. It will look at the files on your computer and infect some of them if it can.


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3.1 Searching for your ancestors

In this section we consider searching for information about your ancestors. We cannot hope to cover all the techniques and information required to research genealogy, family history and local history; there is only time in this unit to scratch the surface. Some of the activities here are open-ended; please do not spend too long on them. If the subject interests you, you can revisit it after the course finishes, making use of the genealogical resources in the Appendix.


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2.8 Reference sourcing quiz

1 When referencing an image what details should be included alongside the image?

  • A The URL of the image

  • B The file name of the image

  • C The image URL
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2.6 Finding images on the Web

As with websites, one of the easiest ways of searching for images is to use a search engine such as Google. You will see that above the Google search box are some words that allow you to select what you are searching for: web, images, groups, news, and more.

7.4 Understanding RFID tags

An RFID tag consists of a microchip and an antenna and some kind of encapsulation, such as epoxy resin, to bind the two together and protect them. Tags come in a variety of shapes and sizes (Figure 20), and are generally one of two main types: active or passive. You
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7.1 Introduction

This section continues with the theme of networked devices by looking at a system of electronic tagging known as Radio Frequency Identity (RFID). In this system, an electronic tag is attached to an object (for example, the pin described in the The Road Ahead extract in the previous section) and an RFID reader is used to interrogate the tag wirelessly and receive information stored on it. We are using the word ‘interrogate’ here because the reader sends out a signal and the tag resp
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6.5 Smart home networks

Some devices in a smart home may need to communicate information about the environment (for example, information about light, heat, humidity, sound, movement, water levels, etc.). They may also need to communicate to:

  • give information about their state (for example, activated, deactivated, faulty);

  • give temporal information (for example clock time, lapsed time, delays);

  • instruct, interrogate or acknowledge another dev
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4.7 WiFi data rates and operating range

Just as for Ethernet, developments in technology have increased the achievable data rates since the first WiFi standard was developed in 1997. At the time of writing, the latest WiFi standard to be published – IEEE 802.11g – defines a data rate of 54 Mbps.

Activity 17: exploratory

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4.6 WiFi stations

A WiFi station determines whether it is in range of an AP by transmitting an enquiry, known as a probe request frame, and waiting for a response. If more than one AP responds, the station will choose to communicate with the one that has the strongest signal. A probe request frame initiates the WiFi connection and is an example of a management frame – a type of frame that does not carry any message data.

Just like the nodes on an Ethernet network, each station must have a means of bein
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4.3 Regulation

Increasing demand for wireless technology means that the radio frequencies must be carefully managed and allocated by governments to satisfy all the different users and to prevent interference between them. (You may remember the UK Government's auction of 3G radio licences in Spring 2000 which raised approximately £22.5 billion.)

Before transmitting radio signals, organisations must usually obtain a licence permitting them to use a specified frequency or band of frequencies. However, o
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4.2 Basic principles of wireless transmission

I've never quite lost the sense of wonder at the way information can be transmitted with no visible link between the sender and recipient. When I was a child I used to think that sound came through the wire linking my family's radio to the mains electricity supply (I was born before the days of battery-powered transistor radios) and I couldn't understand why my parents referred to it as ‘the wireless’ – since clearly it wasn't. I now know that the wire simply fed the radio with the elec
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3.4 Protocols and standards

You have already met the idea of protocols in Section 1 – rules to govern how information is sent, transmitted and received. Protocols can be explained using an analogy with the way people talk to each other. When we talk we don't simply string words together in a random fashion: we have a set of rules (grammar) that determines the order of words and the way sentences are constructed. Understand didn't have other us difficult if it would be quite rules each these for to we. We hope t
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3.3 Wired network configurations

Network nodes can be connected together in different arrangements known as topologies. We are going to describe four common topologies that you may come across.

Figure 10

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2.3 Electromagnetic radiation

To help explain the nature of the waves of energy known as electromagnetic radiation, visualise a pond into which a stone has been thrown. If the state of the pond is ‘frozen’ at an instant in time, the height or depth of the water's surface at that moment will vary with distance from the source of the disturbance. If you were to cut a slice through the pond, you would see a wave shape similar to Author(s): The Open University

Learning outcomes

When you have completed your study of this unit, you should be able to:

  • understand and use correctly terms introduced in this unit in relation to communication networks;

  • understand general principles involved in data exchange between ICT devices;

  • work with numbers expressed in scientific notation, and use the Windows calculator to perform calculations on these numbers.


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Introduction

This unit is from our archive and it is an adapted extract from Networked living: exploring information and communication technologies (T175) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area.

This unit looks at communication systems where devices are th
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Acknowledgements

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Figure 1 ENIAC Computer. Photo © Science Photo Library

Rozin, D. ‘Wooden Mirror’, 2001, IEEE Spectrum, March 2001, p.29. Co
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7.3 Quality of customer service

This is probably the key determinant of customer satisfaction. Most online transactions go through flawlessly. But some don't. Goods fail to arrive, or are delayed, or delivered to the wrong address. Or what is delivered doesn't match what you ordered. With a real-world bricks-and-mortar retailer, the solution is obvious: you phone or turn up at their premises and speak to a human being. But what do you do if an online order goes wrong? Whom do you phone? And where is the number for customer
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4 The eBay phenomenon – what it means

Writers on e-business group Internet processes into four categories, using this grid:

Figure 13
Figure
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2.1 Exploring eBay

First, have a look around the eBay system to get a feel for how it works.

Go to the eBay website

Find an item that interests you, either by clicking on the categories in the left-hand panel …

The Categories displayed on eBay. It starts: Antiques &Art; Automotive (Cars | Classic Cars | Motorc</span><br><span class=Author(s): The Open University

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