1. Module 1… In Touch and Informed
Technology
Module 1… In Touch and Informed

2. Introduction
This book is about:
Technology

3. Computer accept inputs
receive signals from other systems (e.g. via a modem) and convert these signals to data;
process – that is, act on – this data
convert the resulting data back into signals and transmit them;
convert the resulting data into outputs to the user.

4. Computer Hardware Software Program
the collection of physical components
Software
software is the program, or collection of programs, which enables the computer to carry out its tasks
Program
a collection of integrated and interdependent sets of detailed, step-by-step instructions that has been put together to tell a computer how to solve a problem or carry out a task, or part of a task.

5. Computer
A binary code is simply a group of binary digits (also known as ‘bits’) – that is, of 1s and 0s.
A binary code is made up of bits. A binary code that occupies just one byte will be 8 bits long, because there are 8 bits in a byte.
Numbers are often represented as binary codes simply by converting the number to its binary equivalent. Thus 2 is 10 in binary code; 15 is 1111 Sometimes the binary code must be of a fixed length – say 8 bits. In this case zeros are inserted at the front to make up the 8 bits. So 2 is ; 15 is
Another way in which numbers can be represented is by their ASCII equivalent code

6. ASCII --Text Text is usually represented by a sequence of ASCII
ASCII (pronounced ‘askey’) stands for American Standard Code for Information Interchange.
In its standard form of 7 bits it allows for 127 different characters, which is enough for the Latin alphabet, punctuation marks and numerals.
It has various extended forms (8 bits, 255 characters) to allow for accented characters, etc. in various languages.
universal 16-bit code, Unicode, which will be able to support the characters in most of the world’s language scripts. codes, each code representing either an individual letter or a character such as a space, an apostrophe or a digit.

7. Computer--Graphics
A simple line drawing may be represented in the same way as a full-colour picture
but a simpler way is to describe where the lines on the drawing are in some pre-defined way and convert this description to a binary code.
A full-colour picture can be represented by dividing the picture up into tiny squares called pixels or pels and then assigning to each pixel a binary code that describes its colour and brightness.
Sounds, whether speech or music, can be represented by first taking short, equal duration samples of the sound and then using a code to represent the characteristics of each of these samples.
Computer instructions in a program are represented by binary codes that have been laid down by the manufacturer of a particular processor at the time the processor was designed.

8. Computer—Error Handling
Error detection
is a process whereby pieces of binary data are checked while they are being manipulated or transmitted, in order to discover whether an error has occurred.
Error correction
is a process that checks the binary data and if an error has occurred it is corrected
A parity bit-- is an additional bit

9. Hardware for input and output
the purpose of all input peripherals is either to accept an input from a user and convert it to a signal or to accept a signal from another system and convert that signal. Associated with each input peripheral will be an input subsystem which converts the signal from the peripheral to data in a form that the processor can recognize and use

10. Input device—keyboard etc
Keyboards, keypads and buttons
a switch under that key or button is closed and so an electric current can flow.
This produces an electrical signal, but not one in a form which the processor can recognize.
an input subsystem associated with the keyboard detects which key or button has been pressed from the electrical signal produced and then to generate an associated binary code --it is referred to as data or a data word or a binary code or binary data or a binary value.

11. LCD — liquid-crystal display
Monochrome LCD
Contains a thin film of a liquid called Liquid Crystal
Liquid Crystal have rod-shaped molecules
When the voltage is passed the molecules change their alignment
TFT is also known as “Active LCD”
It is sort of a collection of small LCDs, where the pixels are individually turned on or off
The advantage is no flicker

12. LCD — Colour
Colour LCD
have trios of pixels, each pixel having either a red, a green or a blue filter in front.
When a pixel is illuminated, it looks red, green or blue because the light must pass through the filter on its way to the user.
Because all colours can be made up from different combinations of red, green and blue light, any desired shade or colour can be produced by illuminating, in different intensities, the pixels in a trio.

13. LCD — touch sensitive
There are two different methods of making a screen touch-sensitive.
Method-1
The user actually touches a sheet of a type of clear plastic called mylar
separated very slightly from the LCD
The mylar sheet contacts with the glass sheet
Detectors at the edge of the screen are then able to ascertain the co-ordinates of the point where the user touched the screen.
Method-2
has only one layer
has a very low-level acoustic vibration is set up over its surface.
When the user touches the glass, the finger absorbs some of the sound.
This is detected by detectors on the edge of the screen and again a controller is able to ascertain exactly where the user touched the screen.

14. Loudspeakers and buzzers
To produce sound
Sound is produced by vibration
Pitch (Frequency)—when vibration is more the pitch is more– measured in Htz
Loudness (Intensity)—when the object moves to and fro at a greater distance the loud sound is made, if the distance is smaller a quieter sound is produced
Sound in PDA
A tiny piezoelectric ceramic
Can change shape slightly when voltage is applied
If it vibrates fast enough it produces an audible ‘buzz’.

15. Loudspeakers and buzzers
Moving coil loudspeaker
Used for reproducing speech or music
has a cone that is made to vibrate by an electrical signal.
miniature versions can be in PDAs

16. Infrared transmitters
The way in which an infrared signal is transmitted is relatively straightforward
A diode is used which is very similar to the red light-emitting diodes used in many consumer items but which transmits infrared radiation instead of red light.
The infrared radiation produced by this diode is switched rapidly between high and low intensity (‘bright’ and ‘faint’) to produce a stream of pulses of radiation that corresponds to a stream of bits.
An infrared receiver produces an electrical voltage if infrared radiation falls on it, but not otherwise.
It therefore converts the stream of infrared pulses it receives into a stream of electrical pulses which form the bits of a binary signal.

17. Docking Cradles Used for synchronization Use RS232 serial port
Can also use USB (Universal Serial Bus)

18. Memory
It is like set of numbered ‘slots’ called memory locations, or just locations.
The memory address – identifies
Holds exactly same number of bits
data word, is the number of bits that fit in to one location
Most PDAs use 16-bit or 32-bit data words.

19. Bus
It is a data highway
Can be thought of conducting paths connecting two components
Takes all 16 bit of an address of data word to processor or where it is needed
Unidirectional Bus
Address bus
Bidirectional Bus
data bus carries data words between the processor and the main memory.

20. Types of Memory ROM RAM The content can not be changed
Flash ROM the user can change the data
RAM
Random Access memory
It is volatile
PDAs normally have RAM for user data that is the reason for being careful in changing the batteries
Now some PDAs are coming with Flash memory

21. Processor
processors carry out tasks by executing (that is, carrying out), very quickly and in sequence, a list of computer instructions. These instructions tell the processor exactly what it should do, on a step-by-step basis

22. Processor Memory locations are also called registers
The program instructions must refer to the internal register
Different makes of processor have different number of registers and other components may also be different
This is the reason that programs written for one processor will not work for the other type of processor
One way to avoid this problem is to use High Level Programming Language

23. Processor--RISC Reduced instruction set computers
They are always used on PDAs
They work faster
Use less power
Remember the speed of the processor only tells you that how fast the instructions will be fed to the processor
The PDA with color screen needs a faster processor

24. Software operating systems, application program
basic set of programs without which the computer cannot be used
When the computer starts the program that is loaded first is OS
Takes care of input and input
Allows memory mamagement
Enables other programs to be executed
Example: Windows, PalmOS and EPOC32.
application program
Allows the user to do particular tasks

25. Compression
Compression is a process used when files are transferred across the Internet or stored for long time
Compression is a process of recoding binary data into a more compact form.
During the compression process portions of redundant data are detected and removed.
Types of compressions
Lossless--data can be reconstructed exactly later on.
Lossy--data cannot be reconstructed exactly later on. (some information is lost),it is possible to achieve greater compression of the data.
Examples for lossless: ZIP, GIF
Examples for lossy: JPEG, MPEG, MP3

26. The Internet
TCP/IP
Transmission of data across the Internet follows a set of rules, known as a protocol. TCP and IP are the two major protocols used, and they are usually referred to as TCP/IP.
Function of IP
IP stands for Internet Protocol.
Its job is to route data between computers, but it doesn’t check if the data has been received correctly, or even if it has been received at all.
Function of TCP
TCP stands for Transmission Control Protocol,
TCP makes sure that all the data that has been sent has been received, and received correctly.

27. The Internet IP Address IP Address construction IPv6
In order for IP to be able to send data between computers, it needs to be able to identify which computer is which.
every computer connected to the Internet has a unique number known as its IP address.
IP Address construction
IP addresses all consisted of a group of four numbers between 1 and 255. So an IP address might be, for example, The first one, two or three of these numbers indicate which organization, and the remaining numbers indicate which particular computer within that organization.
IPv6
So many computers are now on the Internet that it’s running out of spare IP addresses. So a new version of IP, known as IP version 6 or IPv6, is being introduced. This uses such long IP addresses that there is no fear of them running out in the foreseeable future.

28. Internet and the Web
The Internet is a worldwide network which is made up of a very large number of networks of computers. So it’s a physical entity. You could think of it as hardware.
The Web is an application that uses the Internet. It consists of a very large number of pages of hypertext information stored on computers connected into the Internet and retrievable via other computers connected into the Internet. Although it is not software, it is much more like software than it is like hardware.

29. HTML and XML HTML XML is the language of the webpage writing
It uses tags to control the way graphics and text appear on the webpage on the computer of recipient
It is not searchable though
The searching is done on the basis of the keyword
XML
Very similar to HTML
Does not control the appearance of the document, it controls the content
Search engines can search XML tags and not HTML

30. The

31. Accessing the Internet while on the move
WAP
Wireless application protocol
Facilitates the use of internet by small mobile devices
Aspects to WAP
WML—wireless markup language is specified by WAP
Specifies transport protocol for and web for handheld devices
How does WAP work?
WAP enabled device send the request to ISP
ISP has a Gateway that changes the request from WAP to TCP/IP and sends it to the server with the web page
The webpage passes through the gateway and changes to WAP
WAP does the compression and sends it to device

32. The technology of mobile telephony
Some concepts
Digital signal has finite set of values
Analogue signal can take on any value
Binary signal does not mean the same as the term ‘digital signal’.
All binary signals are digital,but not all digital signals are binary.
A binary signal is restricted to two values; a digital signal to a finite set of values (not necessarily just two).

33. Bandwidth of an analogue signal
Frequency
Is a term used for simple repeating waves. The frequency is the number of times the cycle of the wave repeats in one second.
Bandwidth of an analogue signal
Is the difference between the highest and lowest frequencies present in the signal.
Bandwidth of a binary digital signal
Is normally taken to be the same as the bit rate, that is the number of bits transmitted per second.
Bandwidth of a channel
The maximum range of frequencies the channel can transmit without significant loss of signal strength or distortion of the signals.
Radio spectrum
In mobile telephony, the radio spectrum is a graph (or table) showing how the available radio-frequency ranges are allocated for various purposes and to various telephone companies.

34. PSTN—Public switched telephone Network
It is not possible to connect with direct lines
The telephone subscribers are connected in star network
Switching center is also the telephone exchange

35. PSTN How the local call is made? A calls B
The call goes to switching center– the center checks the location of B
The switching center routs the call from A to B if it is local
If B is non-local the switching center connects it to the National Network
Connection is maintained for the duration of the call connection-oriented.

36. Levels in the switching centers
There are three ‘levels’ of switching centres.
Local switching centres handle local calls directly but connect non-local calls into a national switching centre.
National switching centre--A network of national switching centres handles all non-local national calls but international calls are connected into an international switching centre
International switching center-- from which international connections can be made.

37. Local loop Most telephone network carries digital signals
Most switching centres use digital switching.
The links between a local switching centre and individual subscribers -- mainly analogue.
Voice messages are carried in analogue form in the local loop and then are converted to digital form. Then converted back to analogue for the recipient’s local loop.
This is the reason for the need of the MODEM
The data from the computer is digital
The local loop is analogue
Similarly when the data comes from the local loop it is analogue and needs to be converted to digital

38. Local Loop The maximum bandwidth of the analogue local loop is 3400Hz
The early modems were 34kbps
Now modems are 56kbps

39. ISDN ---ADSL ADSL Basic-rate ISDN
Those who wish to avoid local loop pay more to get ADSL
All the data is transmitted in digital form
The voice is also converted to digital and than transmitted
The bit rate is asymmetric, i.e., the speed of downlink is 512kbps to 2mbps, and uplink is 128kbps to 256kbps
Basic-rate ISDN
Offer two separate 64kbps links or one combined 128kbps
The bit rate is symmetric, i.e., the downlink and uplink are both 64kbps

40. First generation: an analogue system
Frequency division multiple access (FDMA)
Frequency-division’ because the different channels are allocated different, individual frequency bands;
‘multiple-access’ because each channel is accessed by a number of different users when they need.
Early radio telephone had one frequency allocation for each subscriber. The frequency was assigned to only that user and no one else could use it even when the frequency was free
A telephone signal in a given FDMA channel is transmitted using a modulation technique similar to conventional FM radio.
Like conventional FM radio, it can be overheard by anyone with a suitable receiver

41. Mobile Phone
The frequency ranges assigned in Europe are, MHz and MHz
Each user generate a band of frequencies, depending on what is being transmitted
Normally Mobile radio service requires 20kHz bandwidth
If we assign spacing of 25kHz we can only accommodate 1000 users in each direction

42. Mobile Phone

43. Mobile Phone
Path Loss

44. Mobile Phone
Frequency reuse

45. Mobile Phone
Cells

46. Mobile Phone
Microcells

47. Mobile phone
Multipath propagation or fading

48. 2nd generation: GSM System
GSM stands for Global System for Mobile communication
Two organizations involved in standardization are
Conference of European Posts and Telecommunications Administrations (CEPT),
European Telecommunications Standards Institute (ETSI).
GSM is used in Europe, Middle East, Africa, Asia, and America– but it is not the only system
This is the reason why mobile phone bought in one country do not work in other countries, the other reason can be the rang of frequencies used
In North America GSM 1900MHz is also used

49. GSM- digital mobile Mobile station Mobile switching centre (MSC)
Any device used for receiving and transmitting data
Mobile switching centre (MSC)

50. GSM- digital mobile How does MSC where is the mobile phone
Home Location Register (HLR)
Visitor Location Register (VLR)
Sharing the available bandwidth
more widely in frequency – by 200 kHz for GSM
TDMA and FDMA
several telephone signals (often eight in GSM) to be digitized together before transmission. TDMA frame
both the time slots for individual telephone signals and the carrier frequencies have to be allocated and re-allocated to individual users as necessary.

51. GSM- digital mobile TDMA frame synchronization
Lasts for 577 microsecond
Contains 148 bits– only 114 for data
The rest of the bits are used for control purposes
synchronization
Uses digital processing.
A software control is used
the base station monitors the time taken to make a round trip
This information is sent to the mobile as it moves around.
The mobile station then ‘resets’ its internal clock so as to ensure that the bits it transmits arrive at the base station in exactly the correct time slot

52. GSM- digital mobile Bit rate
Digital processing is used which is more like computer speech synthesis
Instead of sampling the speech waveform in the usual way,
the voice signal is analysed to derive the features important for comprehension and recognition of the speaker.
Information about these important features is then transmitted (thus using a far lower bit rate than sending samples of the waveform itself),
and a close replica of the speech signal is then synthesized at the receiving end.

53. GSM- digital mobile Combating fading Adaptive filtering
The mobile device monitors the reception of a special, known sequence of bits transmitted as the central portion of each time slot
This sequence is known as a ‘training sequence’,
It allows the digital circuitry to be ‘trained’ to its best behaviour!
unknown data bits should then also be received correctly.
If necessary the circuit can be ‘re-trained’ every time slot – the technique is known as ‘adaptive filtering’.

54. GSM- digital mobile Frequency hopping
GSM allows for the rapid switching from one carrier frequency to another: frequency hopping.
This takes place so fast, under computer control, that the user is quite unaware of any change.

55. GSM- digital mobile Towards the third generation: 2.5G
general packet radio system (GPRS)
phones are equipped with means for sending and receiving data as packets
seem to the user to be ‘always on’ for non-voice applications.
Unlike a 2G system, the data transfer is not charged according to the duration of the call
but according to the number of packets (that is, the amount of data) transferred.

56. GSM- digital mobile Towards the third generation: 2.5G
GPRS phones are able to handle packet-switched data and circuit-switched voice.
But notice also that there is not yet convergence of distribution, in that data and voice arrive at the platform by these two different types of system, packet-switched and circuit-switched, respectively.
Convergence of distribution will come with the third generation of mobile phones, where everything will be packet-switched.

57. universal mobile telecommunications system (UMTS) -3G mobile
a new system designed to offer information, electronic commerce, entertainment and other interactive voice, data and multimedia services.
the vision of a third generation telecommunications environment where all types of networks whether fixed, mobile or satellite are combined and are interoperable
access services regardless of their terminal and location
The goal of third generation (3G) mobile communication systems is the delivery of multimedia services to the user in the mobile domain
384 kbit/s in microcellular environments and up to 2 Mbit/s in indoor or picocellular environments.’
Why e-commerce?
Internet