Input & Output Devices

Question 1

2D Scanner

Answer 1

Paper placed on a glass panel
Bright light illuminates the document (modern scanners use a xenon light)
Scan head moves across the document
Lens focuses on the document image
Scanned image turned into electric form by the CCD

Question 2

Applications of 2D Scanner

Answer 2

At airports to read passports
OCR software used to read text
Digital camera takes picture of face
Images compared with passport photo using recognition software
Key features compared

Question 3

3D Scanner

Answer 3

Object has x,y coordinates
Scans along coordinates
Scanned image used by CAD

Question 4

Application of 3D Scanners

Answer 4

CT Scanners

MRI Scanners

Question 5

Barcode Scanner

Answer 5

Red laser shone add barcode
Light is reflected back
Sensors detect the light back
Pattern converted to digital
Microprocessor interprets the data
Each digit made up of 2 dark and 2 white lines

Question 6

Stock control

Answer 6

Barcode uniquely identifies product
Stock level stored in DB
Auto reduction of item when sold
Auto reorder level of stock
Can check stock level and location

Question 7

QR Codes

Answer 7

QR Code scanned by camera
Three large squares used to define alignment
Light reflected back
Black squares reflect less than white squares
Squares data is decoded – each square has a binary value
Processed by an app
Links to website or document
QR code can be saved and used again

Question 8

QR Code v Barcode

Answer 8

Barcode 1D QR is 2D
QR code can contain more data
QR code can be read from any angle
QR codes faster to scan than bar codes

Question 9

Digital Cameras

Answer 9

Images converted from analogue to digital using ADC
Image turned to pixels
Each pixel given a value and colour
Pixels form a grid
Pixels stored in sequence
E.g. jpg

Question 10

Keyboards/Concept Keyboard

Answer 10

Circuit board under the keys
Key press completes the circuit
Location of press calculated
Location corresponds to ASCII value
ASCII binary value used by CPU

Question 11

Types of Keyboard

Answer 11

Ergonomic
Virtual
Concept
Brail

Question 12

Microphone

Answer 12

A diaphragm vibrates producing an electric signal

Signal goes to a sound card and is converted into digital values

Question 13

Voice recognition system

Answer 13

Users voice converted into digital signal
Spoken words produce a digital pattern
Software compares wave pattern to patterns stored in memory
If they match person is identified

Question 14

Speech recognition

Answer 14

Spoken words recognized and shown on screen

Problems: The software needs to be trained, Some dialects and accents can cause problems

Question 15

Resistive Touchscreen

Answer 15

Uses multiple layers of material that transmit electric current
When top layer is touched into the lower layer current changes and location is found

Ads
Cheap to make
Can use when wearing a glove

Disads
Poor in sunlight
Easily scratched
Doesn’t allow multi-touch

Question 16

Capacitive

Answer 16

Conductive layer
Current flows from 4 corners – electric field created
Sensors monitor field
When the screen is touched charge is transferred to the finger - current changes and location is calculated

Ads
Good in sunlight
Durable
Allows multi-touch

Disads
The screen can crack on impact
Can’t use wearing gloves
Gloves not conductive – block charge from finger

Question 17

Infra-red

Answer 17

Invisible grid of infra-red beams on screen
When screen is touched beam is broken and location is calculated

Ads
Durable
Allows multi touch
Can use with gloves

Disads
Expensive to make
Screen can crack on impact
Sensitive to dirt

Question 18

Printers

Answer 18

Interrupt - Signal sent to computer about no paper

Buffer – Area of memory used to temporarily store data being sent to the printer

Question 19

Inkjet

Answer 19

Used for low quantities of documents
Used for photographs

Uses liquid ink cartridges
Uses thermal bubble
Rollers used to move the paper
Uses a moving print head
Sprays ink onto the paper
Different colour inks are mixed to create the required colours

Question 20

Laser

Answer 20

Used for high volume quality output

User toner cartridges
Uses charged print drum
Uses static electric charges
Toner is fused to the paper

Question 21

3D

Answer 21

Used to make physical model from blueprint
Used to create physical model from CAD
Uses resin
Solid is built up in thin layers

Direct 3D printing
Uses inkjet technology with a moving head

Binder 3D printing
Similar to direct but uses two passes
1st pass sprays dry powder
2nd pass sprays a binder (type of glue)

Question 22

Speakers & Headphones

Answer 22

Sound produced by passing digital data through a digital to analogue converter (DAC) then through an amplifier
Sound produced by voltage differences vibrating a cone
Rate with which DAC can translate the digital signals is know as sampling rate

Question 23

LCD & LED Screens

Answer 23

Ads over CRT
Brighter image
Higher resolution
Thinner screen
Uses less power
Last longer

Question 24

OLED

Answer 24

Organic layers are thinner, lighter and more flexible
OLED layers can be made from plastic so are lighter
Brighter than LED
No backlighting required so use less power
Can be made into large thin sheets for advertising boards
Very large field of view

Question 25

DLP projector

Answer 25

Uses millions of micro mirrors on a DLP chip
Micro mirrors can switch on/off thousands of times a second
Bright white light passes through colour filter on its way to the DLP chip
Light split into primary colours RGB

Question 26

LCD

Answer 26

Older technology than DLP
Beam of light generated by a bulb
Light sent to group of chromatic-coated mirrors that reflect the light back at different wavelengths corresponding to RGB
Three different light components pass through three LCD screens
Images are then combined using a prism to create full colour image
Finally image passes through projector lens onto a screen