3.3 Focused search sites An alternative to using general purpose search engines is to make use of focused search engines that only index known genealogical sites. For example, the Genealogical Society of the UK and Ireland (GenUKI) provides a search engine. 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. 7.5 Active and passive tags Read the extracts below. Using the information they contain, make notes about the main differences between active and passive RFID tags. You will get more out of this exercise if you make a serious attempt to d 4.4 An introduction to WiFi WiFi (from ‘Wireless Fidelity’) is used to connect devices together in one of two network configurations known as ‘ad hoc’ and ‘infrastructure’. We shall explain these terms shortly. (As a starting point, though, you could look up the terms ‘ad hoc’ and ‘infrastructure’ in your dictionary.) In wireless LANs, nodes are usually referred to as stations – probably because each communicating device acts as a radio station with transmitter and receiver. These func 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 4.1 Introduction The focus of Section 3 was on LANs that use some kind of physical medium (for example, copper wires or fibre-optic cables) to connect together network nodes. In this section we'll be examining wireless networks – that is, networks that transmit data through the air (or space) using radio waves. There's nothing new about wireless: the principles of transmitting information using radio waves were discovered over a century ago. However, using radio waves to provide the transmission links 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 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. 3.1 Introduction This section starts by broadly classifying different types of network, first by the nature of the communication links used to connect devices and then by a network's geographical spread. It then examines in more detail a network which uses a cabled communication link. A networked device is often referred to as a node so we shall use this term in the sections that follow. A node is any device (for example, computer, printer, server) connected to a network, either as an end point ( 2.2 What are signals? To convey data from one point to another we need to represent the data by means of a signal. We can think of a signal as a deliberate variation in some property of the medium used to convey the data. Some examples are: an electrical voltage travelling along copper wires between your telephone and the local exchange; pulses of light (though we might not be able to see them) in a fibre-optic cable; the radio emissions t 1.1 Getting an overview This section starts with an article from a technical journal – the sort that is read by academics and professionals working in a related technical field. It sets the scene for some of the technologies and issues that you will be encountering later in this unit. We're not going to ask you to read the entire article, but we would like you to get an idea of the article's contents, the kind of points the author is making, and the range of issues that it throws up. With this aim in mind, w 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. Acknowledgements The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence
Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: 2 2 Conclusion The versatile tiny transistor is now at the heart of the electronics industry. In the video clips you have seen the history of the incredible shrinking chip, its Scottish connections, and an explanation of the physics that make chips work as well as a reconstruction of making a transistor using the crude techniques of yesteryear. 1 1 The incredible shrinking chip Two Scottish computer engineers with little or no physics knowledge set out to make a semiconductor transistor. This was 50 years ago, and their efforts gained them the Nobel Prize. The versatility of that transistor is now at the heart of the electronics industry. Millions of transistor switches are shrunk down into the microprocessors that are found in computers, mobile phones and almost everything else electrical. The first transistor took years to plan and make; today more are made Introduction This unit focuses on the creation of a semiconductor transistor – a versatile tiny transistor that is now at the heart of the electronics industry. In the video clips, the history of the incredible shrinking chip, its Scottish connections and an explanation of the physics that make chips work are accompanied by a reconstruction of making a transistor using the crude techniques of yesteryear. 7.1 Introduction Earlier on I indicated that in order for a processor to perform a defined function it needs to be supplied with a list of instructions called a program. In this section I shall explore this idea a little further. Software can be split into two categories, application software and operating systems. Application software is the name given to programs which enable a computer to perform specific tasks. The program that processes the image in the digital camera is one example; a word 6 A look to the future So what will computers do for you next? Perhaps they will be the key to solving transport problems. Driverless cars, controlled by computers, are under development. If these ever come to fruition perhaps they could help to reduce the number of road traffic accidents by automatically reducing their speed when they come too close to another car. Or perhaps journeys could be made faster and less frustrating because cars will use communicating computers to analyse traffic density and move along t Introduction There is more to computers and processors than simply PCs. In fact computers are ubiquitous in everyday life. This unit challenges how we view computers through the examples of processors in kitchen scales and digital cameras, as well as a work of art that, at heart, is a computer. This unit is from our archive and is an adapted extract from Computers and processors (T224) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore ot Acknowledgements The content acknowledged below is Proprietary (seeterms and conditions) and is used under licence. This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence All materials included in this unit are derived from content originated at the Open University.
Activity 24
Activity 30: exploratory
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