System Peripherals

Introduction to system peripherals

There are a range of peripherals including the keyboard , Mouse, scanners , monitors, etc in the market.
We could also use modems , sound cards, and VGA cards within our system.
LCD and infrared devices are primarily used in notebook systems.

Key Topics

Keyboards
Mouse
External Storage
Infrared Devices
Scanners
Scanner Variety
Flatbed scanners
Sound Cards

Digital Sound files
Modems
Modulation/Demodulation
VGA Cards
Accelerators
Monitors
CRT
LCD Display

Keyboards

There are a variety of keyboards in the market, from the standard to the specialized ergonomic design
Has two main connectors including the larger Din 5 for older systems and the smaller Din 6 for newer system.
There are two main types of keyboards, the older switch type and the newer capacitive type.
Keyboards are quite cheap and if problems ever arise with them, they can be replaced quite cheaply.
Compressed air cans can be used to clean dirty keyboards.

Mouse

Used to navigate the cursor around screen.
Most operating systems relay on the mouse to make there environment interactive.
Connects either to the PS/2 port, USB port or the serial ports of your system.
The mouse has buttons which when clicked will select the item pointed to on the screen.
Its design contains rollers representing the x and y-axis connected to wheels, which rotate with the rollers.
The roller is rotated with the ball and the wheel has holes within it, which cut a light beam, and the beam cuts are counted.
needs to be cleaned frequently with a cotton swab dampened in alcohol.

Din6 PS/2 and serial Mouse Connector and socket

Infrared Devices

Can be used to support devices such as wireless keyboards, mouse , scanners , and printers .
These infrared devices can be used with both serial and parallel ports .
Some system boards contain a proprietary connection for infrared transceivers, which picks one of the Com port resources .

Scanner

Scanners use a scanning head like a photocopy machine to scan a sheet of paper and obtain a digital image of the contents of the paper.
If the image is graphical it can be manipulated using graphical software ’s, if the image is text it can be converted in to text by Optical Character Recognition (OCR ) programs .
The original scanners were handheld and had a SCSI interface connection.
There are three main types of scanners , Hand held, flatbed, and portable .
The main problem with the handheld scanner is that the scanning head is pushed down on the page that needs to be scanned by hand which takes the smoothness required out of the motion.
The flatbed scanners quickly superceded the hand held scanners because internal motors control the motion of the scanning head.
The flatbed scanner was initially designed with the SCSI interface , but was later upgraded to use the parallel port or a USB port.

The portable scanner can be used with notebook systems and comes in two forms:

One that feeds the paper past the scanning head.
A pen design scanner, which can scan text in to its RAM and transfers data through infrared to the computer system.

Sound Card

The Sound card is used to input , output and change sound and music .
It has three sockets used for speakers , microphone, CD line, and a 15-pin games port at the back.
Most modern systems have a sound card built on the system board
If a sound card is built on system board , the sound card could cause problems with system configuration, therefore it may need to be disabled to allow other devices to be added to the system because onboard devices are configured first.
to be transmitted to the speakers , there is a special connector that connects the sound card to the CDROM.

Digital Sound Files

Sound cards usually deal with MIDI files or WAV files
MIDI = Musical Instrument Digital Interface
WAV =Windows Audio file
MP3 transfers CD quality music over the Internet . You can download MP3 players over the Internet to play the downloaded music.

Sound Card Configuration

Sound cards usually take up several IRQ ’s , IO addresses, DMA ’s when fully configured.
The sound card can be disabled either by changing bios settings or by changing a jumper position on the system board .

ADC on Sound Cards

Sound cards have a Analogue to Digital Converter to convert the analogue sound input in to the computer to digital pulses ready for the system to manipulate.
The bigger the sample sizes in a sound card the more data it can sample, which means it’s a better sound card.

Network Card

Network cards and all other networking components will be explained in full detail in the networking module .

Introduction to Modems

Modem stands for Modulator /Demodulator .
They convert the digital signals from the computer to analogue signals (modulate) to be transmitted over the telephone lines.
They also convert the analogue signals received from the telephone lines to digital signals (demodulate) for the computer to use.
They come in a variety of designs for different mediums including ISDN lines, DSL lines, Cables lines, and Satellite communication .
It uses ADC /DAC Analogue to Digital /Digital to Analogue converters to achieve the task.
Modems come in both internal and external designs.

Modems and UART

Most modems use a UART chip.
UART Stands for Universal Asynchronous Receiver Transmitter.
The UART chip is used either on the system motherboard or on the internal modems to convert the synchronous parallel data to asynchronous serial data ready for transmission.
The conversion for transmission includes Baud rate , start bit , stop bit , data bits , parity bit , and flow control information .
Internal modems require a built in UART chip since they have a built in serial port and connect directly to the ISA or PCI expansion slots .
External modems do not require a UART chip because they connect to the computers serial port that means the system UART has already performed the conversion.
The most popular UART chips are the 8250, 16550 and 82510 for laptop systems. The 16550 are the fastest design with built in data buffering.
The speed of communication on a modem is measured in bits/seconds referred to as baud rate.
Most modems come in speeds ranging from 28.8 kb/s, 33.6kb/s, and 56.6 kb/s
using a special digital compression mechanism for improving performance over a regular telephone line, which is designed only to carry data at 9.6kb/s.

AT Command Set

A standard for modem commands was set by Hayes company which is referred to as the AT command set configuring your modems data transmission information including start bits, stop bits, parity bit , transmission rate.

AT Command Set

Modems Standards

Modems are universally standardized by the International Telecommunications Union (ITU ) to be compatible with each other in communication among the different manufacturers.

Introduction to VGA Cards

All computers have an output peripheral connected to them such as monitors.
Computers send the images to the Monitor through the video card referred to as the VGA card or graphics adapter
A VGA card is essential for computer to work otherwise the computer beeps.
They come in ISA , PCI AGP designs.
In the past video cards were only used for printing text on the screen, now days video card have advanced revolutionarily due to the requirements of the new applications and games software .
Modern SVGA cards have onboard memory , and CPU to reduce the load on the system resources .
The VGA card like all adapters need a software driver in order for the operating system to send the correct signal to the monitor.
Modern video cards have accelerators on board to perform all visual calculations before transferring the image to the monitor.

Monitor Introduction

The monitor works by the same principles as your regular TV with far higher resolution and colors.
Monitors range in size from 12 inch to 21 inch diagonal.
Monitors can be connected to the VGA Card with a 15-pin connector.
There are a variety of output visual devices in the market, which include CRT , based monitors, LCD based monitors, and printers .
Cathode Ray Tube (CRT ) based monitors function by using an electron gun which fires an electron beam towards the phosphorous screen. The electron beam is guided to the correct position on the screen by X and Y magnetic plates. When the beam collides against the phosphorous screen, it lights up producing an image on the screen.

Monitor Resolution

There are 2 main points to consider with monitors, resolution , and refresh rate
The resolution of the monitor is the number of dots that can be fitted on to the screen.

Refresh Rate

The refresh rate is how quickly the electron beam can redraw the screen image. The refresh rate is measured in Hz starting from about 50 to 120Hz or above for better monitors.
If the refresh rate is too slow 50 Hz you will view flicker on the screen but the more modern monitors can be set to fairly high refresh rates.
Non-Interlaced monitors are better monitors because they redraw the whole screen image in one burst making the viewing task a lot easier.
Nearly all monitors sold today are non-interlaced.
The dot pitch of a monitor is the distance between the three-color dots that hit the screen. High quality monitors have a small dot pitch producing high quality dot pitch producing sharper images. A dot pitch of 0.25 indicates a distance of 25 hundredth of a millimeter between the dots on the screen.

LCD Screens

Initially they were only used on notebook systems.
LCD screens are fast becoming very popular in the market despite their price difference.
Now day’s plasma and LCD monitors are becoming very popular due to their lightweight high-resolution flat screen and reduced space consumption. They have yet to reduce in price.
LCD screens use two sheets of polarizing materials with a liquid crystal center. The screen is a mesh grid which lights up at a point where an x and y line are charged thus producing an image on the screen.

Questions

1) What ports can a typical mouse connect to? (choose all that apply)

a) PS/2

b) USB

c) Serial

d) Parallel

e) SCSI

2) What ports can a typical scanner connect to? (choose all that apply)

a) PS/2

b) USB

c) Serial

d) Parallel

e) SCSI

3) Which devices use an analogue to digital converter ADC ?(Choose all that apply)

a) Sound card

b) VGA card

c) Modem

d) Network card

4) What does the command ATZ do?

a) Reset the modem

b) Hang up

c) Control loudness

d) Dial a number

5) What is the resolution of a SVGA card?

a) 640x480

b) 640x200

c) 800x600

d) 720x350

Answers

1. A,B,C

A,B,D,E
A,C,D
A
C